diff -r 000000000000 -r 6474c204b198 js/xpconnect/src/XPCJSRuntime.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/src/XPCJSRuntime.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,3524 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Per JSRuntime object */
+
+#include "mozilla/MemoryReporting.h"
+
+#include "xpcprivate.h"
+#include "xpcpublic.h"
+#include "XPCWrapper.h"
+#include "XPCJSMemoryReporter.h"
+#include "WrapperFactory.h"
+#include "dom_quickstubs.h"
+#include "mozJSComponentLoader.h"
+
+#include "nsIMemoryInfoDumper.h"
+#include "nsIMemoryReporter.h"
+#include "nsIObserverService.h"
+#include "nsIDebug2.h"
+#include "amIAddonManager.h"
+#include "nsPIDOMWindow.h"
+#include "nsPrintfCString.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Services.h"
+
+#include "nsContentUtils.h"
+#include "nsCxPusher.h"
+#include "nsCCUncollectableMarker.h"
+#include "nsCycleCollectionNoteRootCallback.h"
+#include "nsScriptLoader.h"
+#include "jsfriendapi.h"
+#include "jsprf.h"
+#include "js/MemoryMetrics.h"
+#include "js/OldDebugAPI.h"
+#include "mozilla/dom/GeneratedAtomList.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/WindowBinding.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "AccessCheck.h"
+#include "nsGlobalWindow.h"
+#include "nsAboutProtocolUtils.h"
+
+#include "GeckoProfiler.h"
+#include "nsIXULRuntime.h"
+#include "nsJSPrincipals.h"
+
+#ifdef MOZ_CRASHREPORTER
+#include "nsExceptionHandler.h"
+#endif
+
+using namespace mozilla;
+using namespace xpc;
+using namespace JS;
+using mozilla::dom::PerThreadAtomCache;
+
+/***************************************************************************/
+
+const char* const XPCJSRuntime::mStrings[] = {
+    "constructor",          // IDX_CONSTRUCTOR
+    "toString",             // IDX_TO_STRING
+    "toSource",             // IDX_TO_SOURCE
+    "lastResult",           // IDX_LAST_RESULT
+    "returnCode",           // IDX_RETURN_CODE
+    "value",                // IDX_VALUE
+    "QueryInterface",       // IDX_QUERY_INTERFACE
+    "Components",           // IDX_COMPONENTS
+    "wrappedJSObject",      // IDX_WRAPPED_JSOBJECT
+    "Object",               // IDX_OBJECT
+    "Function",             // IDX_FUNCTION
+    "prototype",            // IDX_PROTOTYPE
+    "createInstance",       // IDX_CREATE_INSTANCE
+    "item",                 // IDX_ITEM
+    "__proto__",            // IDX_PROTO
+    "__iterator__",         // IDX_ITERATOR
+    "__exposedProps__",     // IDX_EXPOSEDPROPS
+    "eval",                 // IDX_EVAL
+    "controllers",           // IDX_CONTROLLERS
+};
+
+/***************************************************************************/
+
+static mozilla::Atomic<bool> sDiscardSystemSource(false);
+
+bool
+xpc::ShouldDiscardSystemSource() { return sDiscardSystemSource; }
+
+static void * const UNMARK_ONLY = nullptr;
+static void * const UNMARK_AND_SWEEP = (void *)1;
+
+static PLDHashOperator
+NativeInterfaceSweeper(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                       uint32_t number, void *arg)
+{
+    XPCNativeInterface* iface = ((IID2NativeInterfaceMap::Entry*)hdr)->value;
+    if (iface->IsMarked()) {
+        iface->Unmark();
+        return PL_DHASH_NEXT;
+    }
+
+    if (arg == UNMARK_ONLY)
+        return PL_DHASH_NEXT;
+
+    XPCNativeInterface::DestroyInstance(iface);
+    return PL_DHASH_REMOVE;
+}
+
+// *Some* NativeSets are referenced from mClassInfo2NativeSetMap.
+// *All* NativeSets are referenced from mNativeSetMap.
+// So, in mClassInfo2NativeSetMap we just clear references to the unmarked.
+// In mNativeSetMap we clear the references to the unmarked *and* delete them.
+
+static PLDHashOperator
+NativeUnMarkedSetRemover(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                         uint32_t number, void *arg)
+{
+    XPCNativeSet* set = ((ClassInfo2NativeSetMap::Entry*)hdr)->value;
+    if (set->IsMarked())
+        return PL_DHASH_NEXT;
+    return PL_DHASH_REMOVE;
+}
+
+static PLDHashOperator
+NativeSetSweeper(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                 uint32_t number, void *arg)
+{
+    XPCNativeSet* set = ((NativeSetMap::Entry*)hdr)->key_value;
+    if (set->IsMarked()) {
+        set->Unmark();
+        return PL_DHASH_NEXT;
+    }
+
+    if (arg == UNMARK_ONLY)
+        return PL_DHASH_NEXT;
+
+    XPCNativeSet::DestroyInstance(set);
+    return PL_DHASH_REMOVE;
+}
+
+static PLDHashOperator
+JSClassSweeper(PLDHashTable *table, PLDHashEntryHdr *hdr,
+               uint32_t number, void *arg)
+{
+    XPCNativeScriptableShared* shared =
+        ((XPCNativeScriptableSharedMap::Entry*) hdr)->key;
+    if (shared->IsMarked()) {
+        shared->Unmark();
+        return PL_DHASH_NEXT;
+    }
+
+    if (arg == UNMARK_ONLY)
+        return PL_DHASH_NEXT;
+
+    delete shared;
+    return PL_DHASH_REMOVE;
+}
+
+static PLDHashOperator
+DyingProtoKiller(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                 uint32_t number, void *arg)
+{
+    XPCWrappedNativeProto* proto =
+        (XPCWrappedNativeProto*)((PLDHashEntryStub*)hdr)->key;
+    delete proto;
+    return PL_DHASH_REMOVE;
+}
+
+static PLDHashOperator
+DetachedWrappedNativeProtoMarker(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                                 uint32_t number, void *arg)
+{
+    XPCWrappedNativeProto* proto =
+        (XPCWrappedNativeProto*)((PLDHashEntryStub*)hdr)->key;
+
+    proto->Mark();
+    return PL_DHASH_NEXT;
+}
+
+bool
+XPCJSRuntime::CustomContextCallback(JSContext *cx, unsigned operation)
+{
+    if (operation == JSCONTEXT_NEW) {
+        if (!OnJSContextNew(cx)) {
+            return false;
+        }
+    } else if (operation == JSCONTEXT_DESTROY) {
+        delete XPCContext::GetXPCContext(cx);
+    }
+
+    nsTArray<xpcContextCallback> callbacks(extraContextCallbacks);
+    for (uint32_t i = 0; i < callbacks.Length(); ++i) {
+        if (!callbacks[i](cx, operation)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+class AsyncFreeSnowWhite : public nsRunnable
+{
+public:
+  NS_IMETHOD Run()
+  {
+      TimeStamp start = TimeStamp::Now();
+      bool hadSnowWhiteObjects = nsCycleCollector_doDeferredDeletion();
+      Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_ASYNC_SNOW_WHITE_FREEING,
+                            uint32_t((TimeStamp::Now() - start).ToMilliseconds()));
+      if (hadSnowWhiteObjects && !mContinuation) {
+          mContinuation = true;
+          if (NS_FAILED(NS_DispatchToCurrentThread(this))) {
+              mActive = false;
+          }
+      } else {
+          mActive = false;
+      }
+      return NS_OK;
+  }
+
+  void Dispatch(bool aContinuation = false)
+  {
+      if (mContinuation) {
+          mContinuation = aContinuation;
+      }
+      if (!mActive && NS_SUCCEEDED(NS_DispatchToCurrentThread(this))) {
+          mActive = true;
+      }
+  }
+
+  AsyncFreeSnowWhite() : mContinuation(false), mActive(false) {}
+
+public:
+  bool mContinuation;
+  bool mActive;
+};
+
+namespace xpc {
+
+static uint32_t kLivingAdopters = 0;
+
+void
+RecordAdoptedNode(JSCompartment *c)
+{
+    CompartmentPrivate *priv = EnsureCompartmentPrivate(c);
+    if (!priv->adoptedNode) {
+        priv->adoptedNode = true;
+        ++kLivingAdopters;
+    }
+}
+
+void
+RecordDonatedNode(JSCompartment *c)
+{
+    EnsureCompartmentPrivate(c)->donatedNode = true;
+}
+
+CompartmentPrivate::~CompartmentPrivate()
+{
+    MOZ_COUNT_DTOR(xpc::CompartmentPrivate);
+
+    Telemetry::Accumulate(Telemetry::COMPARTMENT_ADOPTED_NODE, adoptedNode);
+    Telemetry::Accumulate(Telemetry::COMPARTMENT_DONATED_NODE, donatedNode);
+    if (adoptedNode)
+        --kLivingAdopters;
+}
+
+static bool
+TryParseLocationURICandidate(const nsACString& uristr,
+                             CompartmentPrivate::LocationHint aLocationHint,
+                             nsIURI** aURI)
+{
+    static NS_NAMED_LITERAL_CSTRING(kGRE, "resource://gre/");
+    static NS_NAMED_LITERAL_CSTRING(kToolkit, "chrome://global/");
+    static NS_NAMED_LITERAL_CSTRING(kBrowser, "chrome://browser/");
+
+    if (aLocationHint == CompartmentPrivate::LocationHintAddon) {
+        // Blacklist some known locations which are clearly not add-on related.
+        if (StringBeginsWith(uristr, kGRE) ||
+            StringBeginsWith(uristr, kToolkit) ||
+            StringBeginsWith(uristr, kBrowser))
+            return false;
+    }
+
+    nsCOMPtr<nsIURI> uri;
+    if (NS_FAILED(NS_NewURI(getter_AddRefs(uri), uristr)))
+        return false;
+
+    nsAutoCString scheme;
+    if (NS_FAILED(uri->GetScheme(scheme)))
+        return false;
+
+    // Cannot really map data: and blob:.
+    // Also, data: URIs are pretty memory hungry, which is kinda bad
+    // for memory reporter use.
+    if (scheme.EqualsLiteral("data") || scheme.EqualsLiteral("blob"))
+        return false;
+
+    uri.forget(aURI);
+    return true;
+}
+
+bool CompartmentPrivate::TryParseLocationURI(CompartmentPrivate::LocationHint aLocationHint,
+                                             nsIURI **aURI)
+{
+    if (!aURI)
+        return false;
+
+    // Need to parse the URI.
+    if (location.IsEmpty())
+        return false;
+
+    // Handle Sandbox location strings.
+    // A sandbox string looks like this:
+    // <sandboxName> (from: <js-stack-frame-filename>:<lineno>)
+    // where <sandboxName> is user-provided via Cu.Sandbox()
+    // and <js-stack-frame-filename> and <lineno> is the stack frame location
+    // from where Cu.Sandbox was called.
+    // <js-stack-frame-filename> furthermore is "free form", often using a
+    // "uri -> uri -> ..." chain. The following code will and must handle this
+    // common case.
+    // It should be noted that other parts of the code may already rely on the
+    // "format" of these strings, such as the add-on SDK.
+
+    static const nsDependentCString from("(from: ");
+    static const nsDependentCString arrow(" -> ");
+    static const size_t fromLength = from.Length();
+    static const size_t arrowLength = arrow.Length();
+
+    // See: XPCComponents.cpp#AssembleSandboxMemoryReporterName
+    int32_t idx = location.Find(from);
+    if (idx < 0)
+        return TryParseLocationURICandidate(location, aLocationHint, aURI);
+
+
+    // When parsing we're looking for the right-most URI. This URI may be in
+    // <sandboxName>, so we try this first.
+    if (TryParseLocationURICandidate(Substring(location, 0, idx), aLocationHint,
+                                     aURI))
+        return true;
+
+    // Not in <sandboxName> so we need to inspect <js-stack-frame-filename> and
+    // the chain that is potentially contained within and grab the rightmost
+    // item that is actually a URI.
+
+    // First, hack off the :<lineno>) part as well
+    int32_t ridx = location.RFind(NS_LITERAL_CSTRING(":"));
+    nsAutoCString chain(Substring(location, idx + fromLength,
+                                  ridx - idx - fromLength));
+
+    // Loop over the "->" chain. This loop also works for non-chains, or more
+    // correctly chains with only one item.
+    for (;;) {
+        idx = chain.RFind(arrow);
+        if (idx < 0) {
+            // This is the last chain item. Try to parse what is left.
+            return TryParseLocationURICandidate(chain, aLocationHint, aURI);
+        }
+
+        // Try to parse current chain item
+        if (TryParseLocationURICandidate(Substring(chain, idx + arrowLength),
+                                         aLocationHint, aURI))
+            return true;
+
+        // Current chain item couldn't be parsed.
+        // Strip current item and continue.
+        chain = Substring(chain, 0, idx);
+    }
+    MOZ_ASSUME_UNREACHABLE("Chain parser loop does not terminate");
+}
+
+CompartmentPrivate*
+EnsureCompartmentPrivate(JSObject *obj)
+{
+    return EnsureCompartmentPrivate(js::GetObjectCompartment(obj));
+}
+
+CompartmentPrivate*
+EnsureCompartmentPrivate(JSCompartment *c)
+{
+    CompartmentPrivate *priv = GetCompartmentPrivate(c);
+    if (priv)
+        return priv;
+    priv = new CompartmentPrivate(c);
+    JS_SetCompartmentPrivate(c, priv);
+    return priv;
+}
+
+XPCWrappedNativeScope*
+MaybeGetObjectScope(JSObject *obj)
+{
+    MOZ_ASSERT(obj);
+    JSCompartment *compartment = js::GetObjectCompartment(obj);
+
+    MOZ_ASSERT(compartment);
+    CompartmentPrivate *priv = GetCompartmentPrivate(compartment);
+    if (!priv)
+        return nullptr;
+
+    return priv->scope;
+}
+
+static bool
+PrincipalImmuneToScriptPolicy(nsIPrincipal* aPrincipal)
+{
+    // System principal gets a free pass.
+    if (XPCWrapper::GetSecurityManager()->IsSystemPrincipal(aPrincipal))
+        return true;
+
+    // nsExpandedPrincipal gets a free pass.
+    nsCOMPtr<nsIExpandedPrincipal> ep = do_QueryInterface(aPrincipal);
+    if (ep)
+        return true;
+
+    // Check whether our URI is an "about:" URI that allows scripts.  If it is,
+    // we need to allow JS to run.
+    nsCOMPtr<nsIURI> principalURI;
+    aPrincipal->GetURI(getter_AddRefs(principalURI));
+    MOZ_ASSERT(principalURI);
+    bool isAbout;
+    nsresult rv = principalURI->SchemeIs("about", &isAbout);
+    if (NS_SUCCEEDED(rv) && isAbout) {
+        nsCOMPtr<nsIAboutModule> module;
+        rv = NS_GetAboutModule(principalURI, getter_AddRefs(module));
+        if (NS_SUCCEEDED(rv)) {
+            uint32_t flags;
+            rv = module->GetURIFlags(principalURI, &flags);
+            if (NS_SUCCEEDED(rv) &&
+                (flags & nsIAboutModule::ALLOW_SCRIPT)) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+Scriptability::Scriptability(JSCompartment *c) : mScriptBlocks(0)
+                                               , mDocShellAllowsScript(true)
+                                               , mScriptBlockedByPolicy(false)
+{
+    nsIPrincipal *prin = nsJSPrincipals::get(JS_GetCompartmentPrincipals(c));
+    mImmuneToScriptPolicy = PrincipalImmuneToScriptPolicy(prin);
+
+    // If we're not immune, we should have a real principal with a codebase URI.
+    // Check the URI against the new-style domain policy.
+    if (!mImmuneToScriptPolicy) {
+        nsIScriptSecurityManager* ssm = XPCWrapper::GetSecurityManager();
+        nsCOMPtr<nsIURI> codebase;
+        nsresult rv = prin->GetURI(getter_AddRefs(codebase));
+        bool policyAllows;
+        if (NS_SUCCEEDED(rv) && codebase &&
+            NS_SUCCEEDED(ssm->PolicyAllowsScript(codebase, &policyAllows)))
+        {
+            mScriptBlockedByPolicy = !policyAllows;
+        } else {
+            // Something went wrong - be safe and block script.
+            mScriptBlockedByPolicy = true;
+        }
+    }
+}
+
+bool
+Scriptability::Allowed()
+{
+    return mDocShellAllowsScript && !mScriptBlockedByPolicy &&
+           mScriptBlocks == 0;
+}
+
+bool
+Scriptability::IsImmuneToScriptPolicy()
+{
+    return mImmuneToScriptPolicy;
+}
+
+void
+Scriptability::Block()
+{
+    ++mScriptBlocks;
+}
+
+void
+Scriptability::Unblock()
+{
+    MOZ_ASSERT(mScriptBlocks > 0);
+    --mScriptBlocks;
+}
+
+void
+Scriptability::SetDocShellAllowsScript(bool aAllowed)
+{
+    mDocShellAllowsScript = aAllowed || mImmuneToScriptPolicy;
+}
+
+/* static */
+Scriptability&
+Scriptability::Get(JSObject *aScope)
+{
+    return EnsureCompartmentPrivate(aScope)->scriptability;
+}
+
+bool
+IsXBLScope(JSCompartment *compartment)
+{
+    // We always eagerly create compartment privates for XBL scopes.
+    CompartmentPrivate *priv = GetCompartmentPrivate(compartment);
+    if (!priv || !priv->scope)
+        return false;
+    return priv->scope->IsXBLScope();
+}
+
+bool
+IsInXBLScope(JSObject *obj)
+{
+    return IsXBLScope(js::GetObjectCompartment(obj));
+}
+
+bool
+IsUniversalXPConnectEnabled(JSCompartment *compartment)
+{
+    CompartmentPrivate *priv = GetCompartmentPrivate(compartment);
+    if (!priv)
+        return false;
+    return priv->universalXPConnectEnabled;
+}
+
+bool
+IsUniversalXPConnectEnabled(JSContext *cx)
+{
+    JSCompartment *compartment = js::GetContextCompartment(cx);
+    if (!compartment)
+        return false;
+    return IsUniversalXPConnectEnabled(compartment);
+}
+
+bool
+EnableUniversalXPConnect(JSContext *cx)
+{
+    JSCompartment *compartment = js::GetContextCompartment(cx);
+    if (!compartment)
+        return true;
+    // Never set universalXPConnectEnabled on a chrome compartment - it confuses
+    // the security wrapping code.
+    if (AccessCheck::isChrome(compartment))
+        return true;
+    CompartmentPrivate *priv = GetCompartmentPrivate(compartment);
+    if (!priv)
+        return true;
+    priv->universalXPConnectEnabled = true;
+
+    // Recompute all the cross-compartment wrappers leaving the newly-privileged
+    // compartment.
+    bool ok = js::RecomputeWrappers(cx, js::SingleCompartment(compartment),
+                                    js::AllCompartments());
+    NS_ENSURE_TRUE(ok, false);
+
+    // The Components object normally isn't defined for unprivileged web content,
+    // but we define it when UniversalXPConnect is enabled to support legacy
+    // tests.
+    XPCWrappedNativeScope *scope = priv->scope;
+    if (!scope)
+        return true;
+    scope->ForcePrivilegedComponents();
+    return scope->AttachComponentsObject(cx);
+}
+
+JSObject *
+GetJunkScope()
+{
+    XPCJSRuntime *self = nsXPConnect::GetRuntimeInstance();
+    NS_ENSURE_TRUE(self, nullptr);
+    return self->GetJunkScope();
+}
+
+nsIGlobalObject *
+GetJunkScopeGlobal()
+{
+    JSObject *junkScope = GetJunkScope();
+    // GetJunkScope would ideally never fail, currently it is not yet the case
+    // unfortunately...(see Bug 874158)
+    if (!junkScope)
+        return nullptr;
+    return GetNativeForGlobal(junkScope);
+}
+
+JSObject *
+GetCompilationScope()
+{
+    XPCJSRuntime *self = nsXPConnect::GetRuntimeInstance();
+    NS_ENSURE_TRUE(self, nullptr);
+    return self->GetCompilationScope();
+}
+
+JSObject *
+GetSafeJSContextGlobal()
+{
+    return XPCJSRuntime::Get()->GetJSContextStack()->GetSafeJSContextGlobal();
+}
+
+nsGlobalWindow*
+WindowOrNull(JSObject *aObj)
+{
+    MOZ_ASSERT(aObj);
+    MOZ_ASSERT(!js::IsWrapper(aObj));
+
+    // This will always return null until we have Window on WebIDL bindings,
+    // at which point it will do the right thing.
+    if (!IS_WN_CLASS(js::GetObjectClass(aObj))) {
+        nsGlobalWindow* win = nullptr;
+        UNWRAP_OBJECT(Window, aObj, win);
+        return win;
+    }
+
+    nsISupports* supports = XPCWrappedNative::Get(aObj)->GetIdentityObject();
+    nsCOMPtr<nsPIDOMWindow> piWin = do_QueryInterface(supports);
+    if (!piWin)
+        return nullptr;
+    return static_cast<nsGlobalWindow*>(piWin.get());
+}
+
+nsGlobalWindow*
+WindowGlobalOrNull(JSObject *aObj)
+{
+    MOZ_ASSERT(aObj);
+    JSObject *glob = js::GetGlobalForObjectCrossCompartment(aObj);
+
+    return WindowOrNull(glob);
+}
+
+}
+
+static void
+CompartmentDestroyedCallback(JSFreeOp *fop, JSCompartment *compartment)
+{
+    // NB - This callback may be called in JS_DestroyRuntime, which happens
+    // after the XPCJSRuntime has been torn down.
+
+    // Get the current compartment private into an AutoPtr (which will do the
+    // cleanup for us), and null out the private (which may already be null).
+    nsAutoPtr<CompartmentPrivate> priv(GetCompartmentPrivate(compartment));
+    JS_SetCompartmentPrivate(compartment, nullptr);
+}
+
+void XPCJSRuntime::TraceNativeBlackRoots(JSTracer* trc)
+{
+    // Skip this part if XPConnect is shutting down. We get into
+    // bad locking problems with the thread iteration otherwise.
+    if (!nsXPConnect::XPConnect()->IsShuttingDown()) {
+        // Trace those AutoMarkingPtr lists!
+        if (AutoMarkingPtr *roots = Get()->mAutoRoots)
+            roots->TraceJSAll(trc);
+    }
+
+    // XPCJSObjectHolders don't participate in cycle collection, so always
+    // trace them here.
+    XPCRootSetElem *e;
+    for (e = mObjectHolderRoots; e; e = e->GetNextRoot())
+        static_cast<XPCJSObjectHolder*>(e)->TraceJS(trc);
+
+    dom::TraceBlackJS(trc, JS_GetGCParameter(Runtime(), JSGC_NUMBER),
+                      nsXPConnect::XPConnect()->IsShuttingDown());
+}
+
+void XPCJSRuntime::TraceAdditionalNativeGrayRoots(JSTracer *trc)
+{
+    XPCWrappedNativeScope::TraceWrappedNativesInAllScopes(trc, this);
+
+    for (XPCRootSetElem *e = mVariantRoots; e ; e = e->GetNextRoot())
+        static_cast<XPCTraceableVariant*>(e)->TraceJS(trc);
+
+    for (XPCRootSetElem *e = mWrappedJSRoots; e ; e = e->GetNextRoot())
+        static_cast<nsXPCWrappedJS*>(e)->TraceJS(trc);
+}
+
+// static
+void
+XPCJSRuntime::SuspectWrappedNative(XPCWrappedNative *wrapper,
+                                   nsCycleCollectionNoteRootCallback &cb)
+{
+    if (!wrapper->IsValid() || wrapper->IsWrapperExpired())
+        return;
+
+    MOZ_ASSERT(NS_IsMainThread(),
+               "Suspecting wrapped natives from non-main thread");
+
+    // Only record objects that might be part of a cycle as roots, unless
+    // the callback wants all traces (a debug feature).
+    JSObject* obj = wrapper->GetFlatJSObjectPreserveColor();
+    if (xpc_IsGrayGCThing(obj) || cb.WantAllTraces())
+        cb.NoteJSRoot(obj);
+}
+
+void
+XPCJSRuntime::TraverseAdditionalNativeRoots(nsCycleCollectionNoteRootCallback &cb)
+{
+    XPCWrappedNativeScope::SuspectAllWrappers(this, cb);
+
+    for (XPCRootSetElem *e = mVariantRoots; e ; e = e->GetNextRoot()) {
+        XPCTraceableVariant* v = static_cast<XPCTraceableVariant*>(e);
+        if (nsCCUncollectableMarker::InGeneration(cb,
+                                                  v->CCGeneration())) {
+           jsval val = v->GetJSValPreserveColor();
+           if (val.isObject() && !xpc_IsGrayGCThing(&val.toObject()))
+               continue;
+        }
+        cb.NoteXPCOMRoot(v);
+    }
+
+    for (XPCRootSetElem *e = mWrappedJSRoots; e ; e = e->GetNextRoot()) {
+        cb.NoteXPCOMRoot(ToSupports(static_cast<nsXPCWrappedJS*>(e)));
+    }
+}
+
+void
+XPCJSRuntime::UnmarkSkippableJSHolders()
+{
+    CycleCollectedJSRuntime::UnmarkSkippableJSHolders();
+}
+
+void
+XPCJSRuntime::PrepareForForgetSkippable()
+{
+    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+    if (obs) {
+        obs->NotifyObservers(nullptr, "cycle-collector-forget-skippable", nullptr);
+    }
+}
+
+void
+XPCJSRuntime::BeginCycleCollectionCallback()
+{
+    nsJSContext::BeginCycleCollectionCallback();
+
+    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+    if (obs) {
+        obs->NotifyObservers(nullptr, "cycle-collector-begin", nullptr);
+    }
+}
+
+void
+XPCJSRuntime::EndCycleCollectionCallback(CycleCollectorResults &aResults)
+{
+    nsJSContext::EndCycleCollectionCallback(aResults);
+
+    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+    if (obs) {
+        obs->NotifyObservers(nullptr, "cycle-collector-end", nullptr);
+    }
+}
+
+void
+XPCJSRuntime::DispatchDeferredDeletion(bool aContinuation)
+{
+    mAsyncSnowWhiteFreer->Dispatch(aContinuation);
+}
+
+void
+xpc_UnmarkSkippableJSHolders()
+{
+    if (nsXPConnect::XPConnect()->GetRuntime()) {
+        nsXPConnect::XPConnect()->GetRuntime()->UnmarkSkippableJSHolders();
+    }
+}
+
+template<class T> static void
+DoDeferredRelease(nsTArray<T> &array)
+{
+    while (1) {
+        uint32_t count = array.Length();
+        if (!count) {
+            array.Compact();
+            break;
+        }
+        T wrapper = array[count-1];
+        array.RemoveElementAt(count-1);
+        NS_RELEASE(wrapper);
+    }
+}
+
+/* static */ void
+XPCJSRuntime::GCSliceCallback(JSRuntime *rt,
+                              JS::GCProgress progress,
+                              const JS::GCDescription &desc)
+{
+    XPCJSRuntime *self = nsXPConnect::GetRuntimeInstance();
+    if (!self)
+        return;
+
+#ifdef MOZ_CRASHREPORTER
+    CrashReporter::SetGarbageCollecting(progress == JS::GC_CYCLE_BEGIN ||
+                                        progress == JS::GC_SLICE_BEGIN);
+#endif
+
+    if (self->mPrevGCSliceCallback)
+        (*self->mPrevGCSliceCallback)(rt, progress, desc);
+}
+
+void
+XPCJSRuntime::CustomGCCallback(JSGCStatus status)
+{
+    // Record kLivingAdopters once per GC to approximate time sampling during
+    // periods of activity.
+    if (status == JSGC_BEGIN) {
+        Telemetry::Accumulate(Telemetry::COMPARTMENT_LIVING_ADOPTERS,
+                              kLivingAdopters);
+    }
+
+    nsTArray<xpcGCCallback> callbacks(extraGCCallbacks);
+    for (uint32_t i = 0; i < callbacks.Length(); ++i)
+        callbacks[i](status);
+}
+
+/* static */ void
+XPCJSRuntime::FinalizeCallback(JSFreeOp *fop, JSFinalizeStatus status, bool isCompartmentGC)
+{
+    XPCJSRuntime* self = nsXPConnect::GetRuntimeInstance();
+    if (!self)
+        return;
+
+    switch (status) {
+        case JSFINALIZE_GROUP_START:
+        {
+            MOZ_ASSERT(!self->mDoingFinalization, "bad state");
+
+            MOZ_ASSERT(!self->mGCIsRunning, "bad state");
+            self->mGCIsRunning = true;
+
+            nsTArray<nsXPCWrappedJS*>* dyingWrappedJSArray =
+                &self->mWrappedJSToReleaseArray;
+
+            // Add any wrappers whose JSObjects are to be finalized to
+            // this array. Note that we do not want to be changing the
+            // refcount of these wrappers.
+            // We add them to the array now and Release the array members
+            // later to avoid the posibility of doing any JS GCThing
+            // allocations during the gc cycle.
+            self->mWrappedJSMap->FindDyingJSObjects(dyingWrappedJSArray);
+
+            // Find dying scopes.
+            XPCWrappedNativeScope::StartFinalizationPhaseOfGC(fop, self);
+
+            self->mDoingFinalization = true;
+            break;
+        }
+        case JSFINALIZE_GROUP_END:
+        {
+            MOZ_ASSERT(self->mDoingFinalization, "bad state");
+            self->mDoingFinalization = false;
+
+            // Release all the members whose JSObjects are now known
+            // to be dead.
+            DoDeferredRelease(self->mWrappedJSToReleaseArray);
+
+            // Sweep scopes needing cleanup
+            XPCWrappedNativeScope::FinishedFinalizationPhaseOfGC();
+
+            MOZ_ASSERT(self->mGCIsRunning, "bad state");
+            self->mGCIsRunning = false;
+
+            break;
+        }
+        case JSFINALIZE_COLLECTION_END:
+        {
+            MOZ_ASSERT(!self->mGCIsRunning, "bad state");
+            self->mGCIsRunning = true;
+
+            // We use this occasion to mark and sweep NativeInterfaces,
+            // NativeSets, and the WrappedNativeJSClasses...
+
+            // Do the marking...
+            XPCWrappedNativeScope::MarkAllWrappedNativesAndProtos();
+
+            self->mDetachedWrappedNativeProtoMap->
+                Enumerate(DetachedWrappedNativeProtoMarker, nullptr);
+
+            DOM_MarkInterfaces();
+
+            // Mark the sets used in the call contexts. There is a small
+            // chance that a wrapper's set will change *while* a call is
+            // happening which uses that wrapper's old interfface set. So,
+            // we need to do this marking to avoid collecting those sets
+            // that might no longer be otherwise reachable from the wrappers
+            // or the wrapperprotos.
+
+            // Skip this part if XPConnect is shutting down. We get into
+            // bad locking problems with the thread iteration otherwise.
+            if (!nsXPConnect::XPConnect()->IsShuttingDown()) {
+
+                // Mark those AutoMarkingPtr lists!
+                if (AutoMarkingPtr *roots = Get()->mAutoRoots)
+                    roots->MarkAfterJSFinalizeAll();
+
+                XPCCallContext* ccxp = XPCJSRuntime::Get()->GetCallContext();
+                while (ccxp) {
+                    // Deal with the strictness of callcontext that
+                    // complains if you ask for a set when
+                    // it is in a state where the set could not
+                    // possibly be valid.
+                    if (ccxp->CanGetSet()) {
+                        XPCNativeSet* set = ccxp->GetSet();
+                        if (set)
+                            set->Mark();
+                    }
+                    if (ccxp->CanGetInterface()) {
+                        XPCNativeInterface* iface = ccxp->GetInterface();
+                        if (iface)
+                            iface->Mark();
+                    }
+                    ccxp = ccxp->GetPrevCallContext();
+                }
+            }
+
+            // Do the sweeping. During a compartment GC, only
+            // WrappedNativeProtos in collected compartments will be
+            // marked. Therefore, some reachable NativeInterfaces will not be
+            // marked, so it is not safe to sweep them. We still need to unmark
+            // them, since the ones pointed to by WrappedNativeProtos in a
+            // compartment being collected will be marked.
+            //
+            // Ideally, if NativeInterfaces from different compartments were
+            // kept separate, we could sweep only the ones belonging to
+            // compartments being collected. Currently, though, NativeInterfaces
+            // are shared between compartments. This ought to be fixed.
+            void *sweepArg = isCompartmentGC ? UNMARK_ONLY : UNMARK_AND_SWEEP;
+
+            // We don't want to sweep the JSClasses at shutdown time.
+            // At this point there may be JSObjects using them that have
+            // been removed from the other maps.
+            if (!nsXPConnect::XPConnect()->IsShuttingDown()) {
+                self->mNativeScriptableSharedMap->
+                    Enumerate(JSClassSweeper, sweepArg);
+            }
+
+            if (!isCompartmentGC) {
+                self->mClassInfo2NativeSetMap->
+                    Enumerate(NativeUnMarkedSetRemover, nullptr);
+            }
+
+            self->mNativeSetMap->
+                Enumerate(NativeSetSweeper, sweepArg);
+
+            self->mIID2NativeInterfaceMap->
+                Enumerate(NativeInterfaceSweeper, sweepArg);
+
+#ifdef DEBUG
+            XPCWrappedNativeScope::ASSERT_NoInterfaceSetsAreMarked();
+#endif
+
+            // Now we are going to recycle any unused WrappedNativeTearoffs.
+            // We do this by iterating all the live callcontexts
+            // and marking the tearoffs in use. And then we
+            // iterate over all the WrappedNative wrappers and sweep their
+            // tearoffs.
+            //
+            // This allows us to perhaps minimize the growth of the
+            // tearoffs. And also makes us not hold references to interfaces
+            // on our wrapped natives that we are not actually using.
+            //
+            // XXX We may decide to not do this on *every* gc cycle.
+
+            // Skip this part if XPConnect is shutting down. We get into
+            // bad locking problems with the thread iteration otherwise.
+            if (!nsXPConnect::XPConnect()->IsShuttingDown()) {
+                // Do the marking...
+
+                XPCCallContext* ccxp = XPCJSRuntime::Get()->GetCallContext();
+                while (ccxp) {
+                    // Deal with the strictness of callcontext that
+                    // complains if you ask for a tearoff when
+                    // it is in a state where the tearoff could not
+                    // possibly be valid.
+                    if (ccxp->CanGetTearOff()) {
+                        XPCWrappedNativeTearOff* to =
+                            ccxp->GetTearOff();
+                        if (to)
+                            to->Mark();
+                    }
+                    ccxp = ccxp->GetPrevCallContext();
+                }
+
+                // Do the sweeping...
+                XPCWrappedNativeScope::SweepAllWrappedNativeTearOffs();
+            }
+
+            // Now we need to kill the 'Dying' XPCWrappedNativeProtos.
+            // We transfered these native objects to this table when their
+            // JSObject's were finalized. We did not destroy them immediately
+            // at that point because the ordering of JS finalization is not
+            // deterministic and we did not yet know if any wrappers that
+            // might still be referencing the protos where still yet to be
+            // finalized and destroyed. We *do* know that the protos'
+            // JSObjects would not have been finalized if there were any
+            // wrappers that referenced the proto but where not themselves
+            // slated for finalization in this gc cycle. So... at this point
+            // we know that any and all wrappers that might have been
+            // referencing the protos in the dying list are themselves dead.
+            // So, we can safely delete all the protos in the list.
+
+            self->mDyingWrappedNativeProtoMap->
+                Enumerate(DyingProtoKiller, nullptr);
+
+            MOZ_ASSERT(self->mGCIsRunning, "bad state");
+            self->mGCIsRunning = false;
+
+            break;
+        }
+    }
+}
+
+static void WatchdogMain(void *arg);
+class Watchdog;
+class WatchdogManager;
+class AutoLockWatchdog {
+    Watchdog* const mWatchdog;
+  public:
+    AutoLockWatchdog(Watchdog* aWatchdog);
+    ~AutoLockWatchdog();
+};
+
+class Watchdog
+{
+  public:
+    Watchdog(WatchdogManager *aManager)
+      : mManager(aManager)
+      , mLock(nullptr)
+      , mWakeup(nullptr)
+      , mThread(nullptr)
+      , mHibernating(false)
+      , mInitialized(false)
+      , mShuttingDown(false)
+    {}
+    ~Watchdog() { MOZ_ASSERT(!Initialized()); }
+
+    WatchdogManager* Manager() { return mManager; }
+    bool Initialized() { return mInitialized; }
+    bool ShuttingDown() { return mShuttingDown; }
+    PRLock *GetLock() { return mLock; }
+    bool Hibernating() { return mHibernating; }
+    void WakeUp()
+    {
+        MOZ_ASSERT(Initialized());
+        MOZ_ASSERT(Hibernating());
+        mHibernating = false;
+        PR_NotifyCondVar(mWakeup);
+    }
+
+    //
+    // Invoked by the main thread only.
+    //
+
+    void Init()
+    {
+        MOZ_ASSERT(NS_IsMainThread());
+        mLock = PR_NewLock();
+        if (!mLock)
+            NS_RUNTIMEABORT("PR_NewLock failed.");
+        mWakeup = PR_NewCondVar(mLock);
+        if (!mWakeup)
+            NS_RUNTIMEABORT("PR_NewCondVar failed.");
+
+        {
+            AutoLockWatchdog lock(this);
+
+            mThread = PR_CreateThread(PR_USER_THREAD, WatchdogMain, this,
+                                      PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
+                                      PR_UNJOINABLE_THREAD, 0);
+            if (!mThread)
+                NS_RUNTIMEABORT("PR_CreateThread failed!");
+
+            // WatchdogMain acquires the lock and then asserts mInitialized. So
+            // make sure to set mInitialized before releasing the lock here so
+            // that it's atomic with the creation of the thread.
+            mInitialized = true;
+        }
+    }
+
+    void Shutdown()
+    {
+        MOZ_ASSERT(NS_IsMainThread());
+        MOZ_ASSERT(Initialized());
+        {   // Scoped lock.
+            AutoLockWatchdog lock(this);
+
+            // Signal to the watchdog thread that it's time to shut down.
+            mShuttingDown = true;
+
+            // Wake up the watchdog, and wait for it to call us back.
+            PR_NotifyCondVar(mWakeup);
+            PR_WaitCondVar(mWakeup, PR_INTERVAL_NO_TIMEOUT);
+            MOZ_ASSERT(!mShuttingDown);
+        }
+
+        // Destroy state.
+        mThread = nullptr;
+        PR_DestroyCondVar(mWakeup);
+        mWakeup = nullptr;
+        PR_DestroyLock(mLock);
+        mLock = nullptr;
+
+        // All done.
+        mInitialized = false;
+    }
+
+    //
+    // Invoked by the watchdog thread only.
+    //
+
+    void Hibernate()
+    {
+        MOZ_ASSERT(!NS_IsMainThread());
+        mHibernating = true;
+        Sleep(PR_INTERVAL_NO_TIMEOUT);
+    }
+    void Sleep(PRIntervalTime timeout)
+    {
+        MOZ_ASSERT(!NS_IsMainThread());
+        MOZ_ALWAYS_TRUE(PR_WaitCondVar(mWakeup, timeout) == PR_SUCCESS);
+    }
+    void Finished()
+    {
+        MOZ_ASSERT(!NS_IsMainThread());
+        mShuttingDown = false;
+        PR_NotifyCondVar(mWakeup);
+    }
+
+  private:
+    WatchdogManager *mManager;
+
+    PRLock *mLock;
+    PRCondVar *mWakeup;
+    PRThread *mThread;
+    bool mHibernating;
+    bool mInitialized;
+    bool mShuttingDown;
+};
+
+#ifdef MOZ_NUWA_PROCESS
+#include "ipc/Nuwa.h"
+#endif
+
+class WatchdogManager : public nsIObserver
+{
+  public:
+
+    NS_DECL_ISUPPORTS
+    WatchdogManager(XPCJSRuntime *aRuntime) : mRuntime(aRuntime)
+                                            , mRuntimeState(RUNTIME_INACTIVE)
+    {
+        // All the timestamps start at zero except for runtime state change.
+        PodArrayZero(mTimestamps);
+        mTimestamps[TimestampRuntimeStateChange] = PR_Now();
+
+        // Enable the watchdog, if appropriate.
+        RefreshWatchdog();
+
+        // Register ourselves as an observer to get updates on the pref.
+        mozilla::Preferences::AddStrongObserver(this, "dom.use_watchdog");
+    }
+    virtual ~WatchdogManager()
+    {
+        // Shutting down the watchdog requires context-switching to the watchdog
+        // thread, which isn't great to do in a destructor. So we require
+        // consumers to shut it down manually before releasing it.
+        MOZ_ASSERT(!mWatchdog);
+        mozilla::Preferences::RemoveObserver(this, "dom.use_watchdog");
+    }
+
+    NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
+                       const char16_t* aData)
+    {
+        RefreshWatchdog();
+        return NS_OK;
+    }
+
+    // Runtime statistics. These live on the watchdog manager, are written
+    // from the main thread, and are read from the watchdog thread (holding
+    // the lock in each case).
+    void
+    RecordRuntimeActivity(bool active)
+    {
+        // The watchdog reads this state, so acquire the lock before writing it.
+        MOZ_ASSERT(NS_IsMainThread());
+        Maybe<AutoLockWatchdog> lock;
+        if (mWatchdog)
+            lock.construct(mWatchdog);
+
+        // Write state.
+        mTimestamps[TimestampRuntimeStateChange] = PR_Now();
+        mRuntimeState = active ? RUNTIME_ACTIVE : RUNTIME_INACTIVE;
+
+        // The watchdog may be hibernating, waiting for the runtime to go
+        // active. Wake it up if necessary.
+        if (active && mWatchdog && mWatchdog->Hibernating())
+            mWatchdog->WakeUp();
+    }
+    bool IsRuntimeActive() { return mRuntimeState == RUNTIME_ACTIVE; }
+    PRTime TimeSinceLastRuntimeStateChange()
+    {
+        return PR_Now() - GetTimestamp(TimestampRuntimeStateChange);
+    }
+
+    // Note - Because of the runtime activity timestamp, these are read and
+    // written from both threads.
+    void RecordTimestamp(WatchdogTimestampCategory aCategory)
+    {
+        // The watchdog thread always holds the lock when it runs.
+        Maybe<AutoLockWatchdog> maybeLock;
+        if (NS_IsMainThread() && mWatchdog)
+            maybeLock.construct(mWatchdog);
+        mTimestamps[aCategory] = PR_Now();
+    }
+    PRTime GetTimestamp(WatchdogTimestampCategory aCategory)
+    {
+        // The watchdog thread always holds the lock when it runs.
+        Maybe<AutoLockWatchdog> maybeLock;
+        if (NS_IsMainThread() && mWatchdog)
+            maybeLock.construct(mWatchdog);
+        return mTimestamps[aCategory];
+    }
+
+    XPCJSRuntime* Runtime() { return mRuntime; }
+    Watchdog* GetWatchdog() { return mWatchdog; }
+
+    void RefreshWatchdog()
+    {
+        bool wantWatchdog = Preferences::GetBool("dom.use_watchdog", true);
+        if (wantWatchdog == !!mWatchdog)
+            return;
+        if (wantWatchdog)
+            StartWatchdog();
+        else
+            StopWatchdog();
+    }
+
+    void StartWatchdog()
+    {
+        MOZ_ASSERT(!mWatchdog);
+        mWatchdog = new Watchdog(this);
+        mWatchdog->Init();
+    }
+
+    void StopWatchdog()
+    {
+        MOZ_ASSERT(mWatchdog);
+        mWatchdog->Shutdown();
+        mWatchdog = nullptr;
+    }
+
+  private:
+    XPCJSRuntime *mRuntime;
+    nsAutoPtr<Watchdog> mWatchdog;
+
+    enum { RUNTIME_ACTIVE, RUNTIME_INACTIVE } mRuntimeState;
+    PRTime mTimestamps[TimestampCount];
+};
+
+NS_IMPL_ISUPPORTS(WatchdogManager, nsIObserver)
+
+AutoLockWatchdog::AutoLockWatchdog(Watchdog *aWatchdog) : mWatchdog(aWatchdog)
+{
+    PR_Lock(mWatchdog->GetLock());
+}
+
+AutoLockWatchdog::~AutoLockWatchdog()
+{
+    PR_Unlock(mWatchdog->GetLock());
+}
+
+static void
+WatchdogMain(void *arg)
+{
+    PR_SetCurrentThreadName("JS Watchdog");
+
+#ifdef MOZ_NUWA_PROCESS
+    if (IsNuwaProcess()) {
+        NS_ASSERTION(NuwaMarkCurrentThread != nullptr,
+                     "NuwaMarkCurrentThread is undefined!");
+        NuwaMarkCurrentThread(nullptr, nullptr);
+        NuwaFreezeCurrentThread();
+    }
+#endif
+
+    Watchdog* self = static_cast<Watchdog*>(arg);
+    WatchdogManager* manager = self->Manager();
+
+    // Lock lasts until we return
+    AutoLockWatchdog lock(self);
+
+    MOZ_ASSERT(self->Initialized());
+    MOZ_ASSERT(!self->ShuttingDown());
+    while (!self->ShuttingDown()) {
+        // Sleep only 1 second if recently (or currently) active; otherwise, hibernate
+        if (manager->IsRuntimeActive() ||
+            manager->TimeSinceLastRuntimeStateChange() <= PRTime(2*PR_USEC_PER_SEC))
+        {
+            self->Sleep(PR_TicksPerSecond());
+        } else {
+            manager->RecordTimestamp(TimestampWatchdogHibernateStart);
+            self->Hibernate();
+            manager->RecordTimestamp(TimestampWatchdogHibernateStop);
+        }
+
+        // Rise and shine.
+        manager->RecordTimestamp(TimestampWatchdogWakeup);
+
+        // Don't request an interrupt callback if activity started less than one second ago.
+        // The callback is only used for detecting long running scripts, and triggering the
+        // callback from off the main thread can be expensive.
+        if (manager->IsRuntimeActive() &&
+            manager->TimeSinceLastRuntimeStateChange() >= PRTime(PR_USEC_PER_SEC))
+        {
+            bool debuggerAttached = false;
+            nsCOMPtr<nsIDebug2> dbg = do_GetService("@mozilla.org/xpcom/debug;1");
+            if (dbg)
+                dbg->GetIsDebuggerAttached(&debuggerAttached);
+            if (!debuggerAttached)
+                JS_RequestInterruptCallback(manager->Runtime()->Runtime());
+        }
+    }
+
+    // Tell the manager that we've shut down.
+    self->Finished();
+}
+
+PRTime
+XPCJSRuntime::GetWatchdogTimestamp(WatchdogTimestampCategory aCategory)
+{
+    return mWatchdogManager->GetTimestamp(aCategory);
+}
+
+void
+xpc::SimulateActivityCallback(bool aActive)
+{
+    XPCJSRuntime::ActivityCallback(XPCJSRuntime::Get(), aActive);
+}
+
+// static
+JSContext*
+XPCJSRuntime::DefaultJSContextCallback(JSRuntime *rt)
+{
+    MOZ_ASSERT(rt == Get()->Runtime());
+    return Get()->GetJSContextStack()->GetSafeJSContext();
+}
+
+// static
+void
+XPCJSRuntime::ActivityCallback(void *arg, bool active)
+{
+    XPCJSRuntime* self = static_cast<XPCJSRuntime*>(arg);
+    self->mWatchdogManager->RecordRuntimeActivity(active);
+}
+
+// static
+//
+// JS-CTypes creates and caches a JSContext that it uses when executing JS
+// callbacks. When we're notified that ctypes is about to call into some JS,
+// push the cx to maintain the integrity of the context stack.
+void
+XPCJSRuntime::CTypesActivityCallback(JSContext *cx, js::CTypesActivityType type)
+{
+  if (type == js::CTYPES_CALLBACK_BEGIN) {
+    if (!xpc::PushJSContextNoScriptContext(cx))
+      MOZ_CRASH();
+  } else if (type == js::CTYPES_CALLBACK_END) {
+    xpc::PopJSContextNoScriptContext();
+  }
+}
+
+// static
+bool
+XPCJSRuntime::InterruptCallback(JSContext *cx)
+{
+    XPCJSRuntime *self = XPCJSRuntime::Get();
+
+    // If this is the first time the interrupt callback has fired since we last
+    // returned to the event loop, mark the checkpoint.
+    if (self->mSlowScriptCheckpoint.IsNull()) {
+        self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
+        return true;
+    }
+
+    // This is at least the second interrupt callback we've received since
+    // returning to the event loop. See how long it's been, and what the limit
+    // is.
+    TimeDuration duration = TimeStamp::NowLoRes() - self->mSlowScriptCheckpoint;
+    bool chrome =
+      nsContentUtils::IsSystemPrincipal(nsContentUtils::GetSubjectPrincipal());
+    const char *prefName = chrome ? "dom.max_chrome_script_run_time"
+                                  : "dom.max_script_run_time";
+    int32_t limit = Preferences::GetInt(prefName, chrome ? 20 : 10);
+
+    // If there's no limit, or we're within the limit, let it go.
+    if (limit == 0 || duration.ToSeconds() < limit)
+        return true;
+
+    //
+    // This has gone on long enough! Time to take action. ;-)
+    //
+
+    // Get the DOM window associated with the running script. If the script is
+    // running in a non-DOM scope, we have to just let it keep running.
+    RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+    nsRefPtr<nsGlobalWindow> win = WindowOrNull(global);
+    if (!win && IsSandbox(global)) {
+        // If this is a sandbox associated with a DOMWindow via a
+        // sandboxPrototype, use that DOMWindow. This supports GreaseMonkey
+        // and JetPack content scripts.
+        JS::Rooted<JSObject*> proto(cx);
+        if (!JS_GetPrototype(cx, global, &proto))
+            return false;
+        if (proto && IsSandboxPrototypeProxy(proto) &&
+            (proto = js::CheckedUnwrap(proto, /* stopAtOuter = */ false)))
+        {
+            win = WindowGlobalOrNull(proto);
+        }
+    }
+    if (!win)
+        return true;
+
+    // Show the prompt to the user, and kill if requested.
+    nsGlobalWindow::SlowScriptResponse response = win->ShowSlowScriptDialog();
+    if (response == nsGlobalWindow::KillSlowScript)
+        return false;
+
+    // The user chose to continue the script. Reset the timer, and disable this
+    // machinery with a pref of the user opted out of future slow-script dialogs.
+    self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
+    if (response == nsGlobalWindow::AlwaysContinueSlowScript)
+        Preferences::SetInt(prefName, 0);
+
+    return true;
+}
+
+/* static */ void
+XPCJSRuntime::OutOfMemoryCallback(JSContext *cx)
+{
+    if (!Preferences::GetBool("memory.dump_reports_on_oom")) {
+        return;
+    }
+
+    nsCOMPtr<nsIMemoryInfoDumper> dumper =
+        do_GetService("@mozilla.org/memory-info-dumper;1");
+    if (!dumper) {
+        return;
+    }
+
+    // If this fails, it fails silently.
+    dumper->DumpMemoryInfoToTempDir(NS_LITERAL_STRING("due-to-JS-OOM"),
+                                    /* minimizeMemoryUsage = */ false);
+}
+
+size_t
+XPCJSRuntime::SizeOfIncludingThis(MallocSizeOf mallocSizeOf)
+{
+    size_t n = 0;
+    n += mallocSizeOf(this);
+    n += mWrappedJSMap->SizeOfIncludingThis(mallocSizeOf);
+    n += mIID2NativeInterfaceMap->SizeOfIncludingThis(mallocSizeOf);
+    n += mClassInfo2NativeSetMap->ShallowSizeOfIncludingThis(mallocSizeOf);
+    n += mNativeSetMap->SizeOfIncludingThis(mallocSizeOf);
+
+    n += CycleCollectedJSRuntime::SizeOfExcludingThis(mallocSizeOf);
+
+    // There are other XPCJSRuntime members that could be measured; the above
+    // ones have been seen by DMD to be worth measuring.  More stuff may be
+    // added later.
+
+    return n;
+}
+
+nsString*
+XPCJSRuntime::NewShortLivedString()
+{
+    for (uint32_t i = 0; i < XPCCCX_STRING_CACHE_SIZE; ++i) {
+        if (mScratchStrings[i].empty()) {
+            mScratchStrings[i].construct();
+            return mScratchStrings[i].addr();
+        }
+    }
+
+    // All our internal string wrappers are used, allocate a new string.
+    return new nsString();
+}
+
+void
+XPCJSRuntime::DeleteShortLivedString(nsString *string)
+{
+    if (string == &EmptyString() || string == &NullString())
+        return;
+
+    for (uint32_t i = 0; i < XPCCCX_STRING_CACHE_SIZE; ++i) {
+        if (!mScratchStrings[i].empty() &&
+            mScratchStrings[i].addr() == string) {
+            // One of our internal strings is no longer in use, mark
+            // it as such and free its data.
+            mScratchStrings[i].destroy();
+            return;
+        }
+    }
+
+    // We're done with a string that's not one of our internal
+    // strings, delete it.
+    delete string;
+}
+
+/***************************************************************************/
+
+static PLDHashOperator
+DetachedWrappedNativeProtoShutdownMarker(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                                         uint32_t number, void *arg)
+{
+    XPCWrappedNativeProto* proto =
+        (XPCWrappedNativeProto*)((PLDHashEntryStub*)hdr)->key;
+
+    proto->SystemIsBeingShutDown();
+    return PL_DHASH_NEXT;
+}
+
+void XPCJSRuntime::DestroyJSContextStack()
+{
+    delete mJSContextStack;
+    mJSContextStack = nullptr;
+}
+
+void XPCJSRuntime::SystemIsBeingShutDown()
+{
+    DOM_ClearInterfaces();
+
+    if (mDetachedWrappedNativeProtoMap)
+        mDetachedWrappedNativeProtoMap->
+            Enumerate(DetachedWrappedNativeProtoShutdownMarker, nullptr);
+}
+
+#define JS_OPTIONS_DOT_STR "javascript.options."
+
+static void
+ReloadPrefsCallback(const char *pref, void *data)
+{
+    XPCJSRuntime *runtime = reinterpret_cast<XPCJSRuntime *>(data);
+    JSRuntime *rt = runtime->Runtime();
+
+    bool safeMode = false;
+    nsCOMPtr<nsIXULRuntime> xr = do_GetService("@mozilla.org/xre/runtime;1");
+    if (xr) {
+        xr->GetInSafeMode(&safeMode);
+    }
+
+    bool useBaseline = Preferences::GetBool(JS_OPTIONS_DOT_STR "baselinejit") && !safeMode;
+    bool useIon = Preferences::GetBool(JS_OPTIONS_DOT_STR "ion") && !safeMode;
+    bool useAsmJS = Preferences::GetBool(JS_OPTIONS_DOT_STR "asmjs") && !safeMode;
+
+    bool parallelParsing = Preferences::GetBool(JS_OPTIONS_DOT_STR "parallel_parsing");
+    bool parallelIonCompilation = Preferences::GetBool(JS_OPTIONS_DOT_STR
+                                                       "ion.parallel_compilation");
+    bool useBaselineEager = Preferences::GetBool(JS_OPTIONS_DOT_STR
+                                                 "baselinejit.unsafe_eager_compilation");
+    bool useIonEager = Preferences::GetBool(JS_OPTIONS_DOT_STR "ion.unsafe_eager_compilation");
+
+    sDiscardSystemSource = Preferences::GetBool(JS_OPTIONS_DOT_STR "discardSystemSource");
+
+    JS::RuntimeOptionsRef(rt).setBaseline(useBaseline)
+                             .setIon(useIon)
+                           .  setAsmJS(useAsmJS);
+
+    JS_SetParallelParsingEnabled(rt, parallelParsing);
+    JS_SetParallelIonCompilationEnabled(rt, parallelIonCompilation);
+    JS_SetGlobalJitCompilerOption(rt, JSJITCOMPILER_BASELINE_USECOUNT_TRIGGER,
+                                  useBaselineEager ? 0 : -1);
+    JS_SetGlobalJitCompilerOption(rt, JSJITCOMPILER_ION_USECOUNT_TRIGGER,
+                                  useIonEager ? 0 : -1);
+}
+
+XPCJSRuntime::~XPCJSRuntime()
+{
+    // This destructor runs before ~CycleCollectedJSRuntime, which does the
+    // actual JS_DestroyRuntime() call. But destroying the runtime triggers
+    // one final GC, which can call back into the runtime with various
+    // callback if we aren't careful. Null out the relevant callbacks.
+    js::SetActivityCallback(Runtime(), nullptr, nullptr);
+    JS_SetFinalizeCallback(Runtime(), nullptr);
+
+    // Clear any pending exception.  It might be an XPCWrappedJS, and if we try
+    // to destroy it later we will crash.
+    SetPendingException(nullptr);
+
+    JS::SetGCSliceCallback(Runtime(), mPrevGCSliceCallback);
+
+    xpc_DelocalizeRuntime(Runtime());
+
+    if (mWatchdogManager->GetWatchdog())
+        mWatchdogManager->StopWatchdog();
+
+    if (mCallContext)
+        mCallContext->SystemIsBeingShutDown();
+
+    auto rtPrivate = static_cast<PerThreadAtomCache*>(JS_GetRuntimePrivate(Runtime()));
+    delete rtPrivate;
+    JS_SetRuntimePrivate(Runtime(), nullptr);
+
+    // clean up and destroy maps...
+    if (mWrappedJSMap) {
+        mWrappedJSMap->ShutdownMarker();
+        delete mWrappedJSMap;
+        mWrappedJSMap = nullptr;
+    }
+
+    if (mWrappedJSClassMap) {
+        delete mWrappedJSClassMap;
+        mWrappedJSClassMap = nullptr;
+    }
+
+    if (mIID2NativeInterfaceMap) {
+        delete mIID2NativeInterfaceMap;
+        mIID2NativeInterfaceMap = nullptr;
+    }
+
+    if (mClassInfo2NativeSetMap) {
+        delete mClassInfo2NativeSetMap;
+        mClassInfo2NativeSetMap = nullptr;
+    }
+
+    if (mNativeSetMap) {
+        delete mNativeSetMap;
+        mNativeSetMap = nullptr;
+    }
+
+    if (mThisTranslatorMap) {
+        delete mThisTranslatorMap;
+        mThisTranslatorMap = nullptr;
+    }
+
+    if (mNativeScriptableSharedMap) {
+        delete mNativeScriptableSharedMap;
+        mNativeScriptableSharedMap = nullptr;
+    }
+
+    if (mDyingWrappedNativeProtoMap) {
+        delete mDyingWrappedNativeProtoMap;
+        mDyingWrappedNativeProtoMap = nullptr;
+    }
+
+    if (mDetachedWrappedNativeProtoMap) {
+        delete mDetachedWrappedNativeProtoMap;
+        mDetachedWrappedNativeProtoMap = nullptr;
+    }
+
+#ifdef MOZ_ENABLE_PROFILER_SPS
+    // Tell the profiler that the runtime is gone
+    if (PseudoStack *stack = mozilla_get_pseudo_stack())
+        stack->sampleRuntime(nullptr);
+#endif
+
+#ifdef DEBUG
+    for (uint32_t i = 0; i < XPCCCX_STRING_CACHE_SIZE; ++i) {
+        MOZ_ASSERT(mScratchStrings[i].empty(), "Short lived string still in use");
+    }
+#endif
+
+    Preferences::UnregisterCallback(ReloadPrefsCallback, JS_OPTIONS_DOT_STR, this);
+}
+
+static void
+GetCompartmentName(JSCompartment *c, nsCString &name, bool replaceSlashes)
+{
+    if (js::IsAtomsCompartment(c)) {
+        name.AssignLiteral("atoms");
+    } else if (JSPrincipals *principals = JS_GetCompartmentPrincipals(c)) {
+        nsJSPrincipals::get(principals)->GetScriptLocation(name);
+
+        // If the compartment's location (name) differs from the principal's
+        // script location, append the compartment's location to allow
+        // differentiation of multiple compartments owned by the same principal
+        // (e.g. components owned by the system or null principal).
+        CompartmentPrivate *compartmentPrivate = GetCompartmentPrivate(c);
+        if (compartmentPrivate) {
+            const nsACString& location = compartmentPrivate->GetLocation();
+            if (!location.IsEmpty() && !location.Equals(name)) {
+                name.AppendLiteral(", ");
+                name.Append(location);
+            }
+        }
+
+        // A hack: replace forward slashes with '\\' so they aren't
+        // treated as path separators.  Users of the reporters
+        // (such as about:memory) have to undo this change.
+        if (replaceSlashes)
+            name.ReplaceChar('/', '\\');
+    } else {
+        name.AssignLiteral("null-principal");
+    }
+}
+
+static int64_t
+JSMainRuntimeGCHeapDistinguishedAmount()
+{
+    JSRuntime *rt = nsXPConnect::GetRuntimeInstance()->Runtime();
+    return int64_t(JS_GetGCParameter(rt, JSGC_TOTAL_CHUNKS)) *
+           js::gc::ChunkSize;
+}
+
+static int64_t
+JSMainRuntimeTemporaryPeakDistinguishedAmount()
+{
+    JSRuntime *rt = nsXPConnect::GetRuntimeInstance()->Runtime();
+    return JS::PeakSizeOfTemporary(rt);
+}
+
+static int64_t
+JSMainRuntimeCompartmentsSystemDistinguishedAmount()
+{
+    JSRuntime *rt = nsXPConnect::GetRuntimeInstance()->Runtime();
+    return JS::SystemCompartmentCount(rt);
+}
+
+static int64_t
+JSMainRuntimeCompartmentsUserDistinguishedAmount()
+{
+    JSRuntime *rt = nsXPConnect::GetRuntimeInstance()->Runtime();
+    return JS::UserCompartmentCount(rt);
+}
+
+class JSMainRuntimeTemporaryPeakReporter MOZ_FINAL : public nsIMemoryReporter
+{
+  public:
+    NS_DECL_ISUPPORTS
+
+    NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
+                              nsISupports* aData)
+    {
+        return MOZ_COLLECT_REPORT("js-main-runtime-temporary-peak",
+            KIND_OTHER, UNITS_BYTES,
+            JSMainRuntimeTemporaryPeakDistinguishedAmount(),
+            "Peak transient data size in the main JSRuntime (the current size "
+            "of which is reported as "
+            "'explicit/js-non-window/runtime/temporary').");
+    }
+};
+
+NS_IMPL_ISUPPORTS(JSMainRuntimeTemporaryPeakReporter, nsIMemoryReporter)
+
+// The REPORT* macros do an unconditional report.  The ZCREPORT* macros are for
+// compartments and zones; they aggregate any entries smaller than
+// SUNDRIES_THRESHOLD into the "sundries/gc-heap" and "sundries/malloc-heap"
+// entries for the compartment.
+
+#define SUNDRIES_THRESHOLD js::MemoryReportingSundriesThreshold()
+
+#define REPORT(_path, _kind, _units, _amount, _desc)                          \
+    do {                                                                      \
+        nsresult rv;                                                          \
+        rv = cb->Callback(EmptyCString(), _path,                              \
+                          nsIMemoryReporter::_kind,                           \
+                          nsIMemoryReporter::_units,                          \
+                          _amount,                                            \
+                          NS_LITERAL_CSTRING(_desc),                          \
+                          closure);                                           \
+        NS_ENSURE_SUCCESS(rv, rv);                                            \
+    } while (0)
+
+#define REPORT_BYTES(_path, _kind, _amount, _desc)                            \
+    REPORT(_path, _kind, UNITS_BYTES, _amount, _desc);
+
+#define REPORT_GC_BYTES(_path, _amount, _desc)                                \
+    do {                                                                      \
+        size_t amount = _amount;  /* evaluate _amount only once */            \
+        nsresult rv;                                                          \
+        rv = cb->Callback(EmptyCString(), _path,                              \
+                          nsIMemoryReporter::KIND_NONHEAP,                    \
+                          nsIMemoryReporter::UNITS_BYTES, amount,             \
+                          NS_LITERAL_CSTRING(_desc), closure);                \
+        NS_ENSURE_SUCCESS(rv, rv);                                            \
+        gcTotal += amount;                                                    \
+    } while (0)
+
+// Report compartment/zone non-GC (KIND_HEAP) bytes.
+#define ZCREPORT_BYTES(_path, _amount, _desc)                                 \
+    do {                                                                      \
+        /* Assign _descLiteral plus "" into a char* to prove that it's */     \
+        /* actually a literal. */                                             \
+        size_t amount = _amount;  /* evaluate _amount only once */            \
+        if (amount >= SUNDRIES_THRESHOLD) {                                   \
+            nsresult rv;                                                      \
+            rv = cb->Callback(EmptyCString(), _path,                          \
+                              nsIMemoryReporter::KIND_HEAP,                   \
+                              nsIMemoryReporter::UNITS_BYTES, amount,         \
+                              NS_LITERAL_CSTRING(_desc), closure);            \
+            NS_ENSURE_SUCCESS(rv, rv);                                        \
+        } else {                                                              \
+            sundriesMallocHeap += amount;                                     \
+        }                                                                     \
+    } while (0)
+
+// Report compartment/zone GC bytes.
+#define ZCREPORT_GC_BYTES(_path, _amount, _desc)                              \
+    do {                                                                      \
+        size_t amount = _amount;  /* evaluate _amount only once */            \
+        if (amount >= SUNDRIES_THRESHOLD) {                                   \
+            nsresult rv;                                                      \
+            rv = cb->Callback(EmptyCString(), _path,                          \
+                              nsIMemoryReporter::KIND_NONHEAP,                \
+                              nsIMemoryReporter::UNITS_BYTES, amount,         \
+                              NS_LITERAL_CSTRING(_desc), closure);            \
+            NS_ENSURE_SUCCESS(rv, rv);                                        \
+            gcTotal += amount;                                                \
+        } else {                                                              \
+            sundriesGCHeap += amount;                                         \
+        }                                                                     \
+    } while (0)
+
+// Report runtime bytes.
+#define RREPORT_BYTES(_path, _kind, _amount, _desc)                           \
+    do {                                                                      \
+        size_t amount = _amount;  /* evaluate _amount only once */            \
+        nsresult rv;                                                          \
+        rv = cb->Callback(EmptyCString(), _path,                              \
+                          nsIMemoryReporter::_kind,                           \
+                          nsIMemoryReporter::UNITS_BYTES, amount,             \
+                          NS_LITERAL_CSTRING(_desc), closure);                \
+        NS_ENSURE_SUCCESS(rv, rv);                                            \
+        rtTotal += amount;                                                    \
+    } while (0)
+
+MOZ_DEFINE_MALLOC_SIZE_OF(JSMallocSizeOf)
+
+namespace xpc {
+
+static nsresult
+ReportZoneStats(const JS::ZoneStats &zStats,
+                const xpc::ZoneStatsExtras &extras,
+                nsIMemoryReporterCallback *cb,
+                nsISupports *closure, size_t *gcTotalOut = nullptr)
+{
+    const nsAutoCString& pathPrefix = extras.pathPrefix;
+    size_t gcTotal = 0, sundriesGCHeap = 0, sundriesMallocHeap = 0;
+
+    MOZ_ASSERT(!gcTotalOut == zStats.isTotals);
+
+    ZCREPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("gc-heap-arena-admin"),
+        zStats.gcHeapArenaAdmin,
+        "Bookkeeping information and alignment padding within GC arenas.");
+
+    ZCREPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("unused-gc-things"),
+        zStats.unusedGCThings,
+        "Empty GC thing cells within non-empty arenas.");
+
+    ZCREPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("lazy-scripts/gc-heap"),
+        zStats.lazyScriptsGCHeap,
+        "Scripts that haven't executed yet.");
+
+    ZCREPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("lazy-scripts/malloc-heap"),
+        zStats.lazyScriptsMallocHeap,
+        "Lazy script tables containing free variables or inner functions.");
+
+    ZCREPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("jit-codes-gc-heap"),
+        zStats.jitCodesGCHeap,
+        "References to executable code pools used by the JITs.");
+
+    ZCREPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("type-objects/gc-heap"),
+        zStats.typeObjectsGCHeap,
+        "Type inference information about objects.");
+
+    ZCREPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("type-objects/malloc-heap"),
+        zStats.typeObjectsMallocHeap,
+        "Type object addenda.");
+
+    ZCREPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("type-pool"),
+        zStats.typePool,
+        "Type sets and related data.");
+
+    ZCREPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("baseline/optimized-stubs"),
+        zStats.baselineStubsOptimized,
+        "The Baseline JIT's optimized IC stubs (excluding code).");
+
+    size_t stringsNotableAboutMemoryGCHeap = 0;
+    size_t stringsNotableAboutMemoryMallocHeap = 0;
+
+    #define MAYBE_INLINE \
+        "The characters may be inline or on the malloc heap."
+    #define MAYBE_OVERALLOCATED \
+        "Sometimes over-allocated to simplify string concatenation."
+
+    for (size_t i = 0; i < zStats.notableStrings.length(); i++) {
+        const JS::NotableStringInfo& info = zStats.notableStrings[i];
+
+        MOZ_ASSERT(!zStats.isTotals);
+
+        nsDependentCString notableString(info.buffer);
+
+        // Viewing about:memory generates many notable strings which contain
+        // "string(length=".  If we report these as notable, then we'll create
+        // even more notable strings the next time we open about:memory (unless
+        // there's a GC in the meantime), and so on ad infinitum.
+        //
+        // To avoid cluttering up about:memory like this, we stick notable
+        // strings which contain "string(length=" into their own bucket.
+#       define STRING_LENGTH "string(length="
+        if (FindInReadable(NS_LITERAL_CSTRING(STRING_LENGTH), notableString)) {
+            stringsNotableAboutMemoryGCHeap += info.gcHeap;
+            stringsNotableAboutMemoryMallocHeap += info.mallocHeap;
+            continue;
+        }
+
+        // Escape / to \ before we put notableString into the memory reporter
+        // path, because we don't want any forward slashes in the string to
+        // count as path separators.
+        nsCString escapedString(notableString);
+        escapedString.ReplaceSubstring("/", "\\");
+
+        bool truncated = notableString.Length() < info.length;
+
+        nsCString path = pathPrefix +
+            nsPrintfCString("strings/" STRING_LENGTH "%d, copies=%d, \"%s\"%s)/",
+                            info.length, info.numCopies, escapedString.get(),
+                            truncated ? " (truncated)" : "");
+
+        if (info.gcHeap > 0) {
+            REPORT_GC_BYTES(path + NS_LITERAL_CSTRING("gc-heap"),
+                info.gcHeap,
+                "Strings. " MAYBE_INLINE);
+        }
+
+        if (info.mallocHeap > 0) {
+            REPORT_BYTES(path + NS_LITERAL_CSTRING("malloc-heap"),
+                KIND_HEAP, info.mallocHeap,
+                "Non-inline string characters. " MAYBE_OVERALLOCATED);
+        }
+    }
+
+    nsCString nonNotablePath = pathPrefix;
+    nonNotablePath += zStats.isTotals
+                    ? NS_LITERAL_CSTRING("strings/")
+                    : NS_LITERAL_CSTRING("strings/string(<non-notable strings>)/");
+
+    if (zStats.stringInfo.gcHeap > 0) {
+        REPORT_GC_BYTES(nonNotablePath + NS_LITERAL_CSTRING("gc-heap"),
+            zStats.stringInfo.gcHeap,
+            "Strings. " MAYBE_INLINE);
+    }
+
+    if (zStats.stringInfo.mallocHeap > 0) {
+        REPORT_BYTES(nonNotablePath + NS_LITERAL_CSTRING("malloc-heap"),
+            KIND_HEAP, zStats.stringInfo.mallocHeap,
+            "Non-inline string characters. " MAYBE_OVERALLOCATED);
+    }
+
+    if (stringsNotableAboutMemoryGCHeap > 0) {
+        MOZ_ASSERT(!zStats.isTotals);
+        REPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("strings/string(<about-memory>)/gc-heap"),
+            stringsNotableAboutMemoryGCHeap,
+            "Strings that contain the characters '" STRING_LENGTH "', which "
+            "are probably from about:memory itself." MAYBE_INLINE
+            " We filter them out rather than display them, because displaying "
+            "them would create even more such strings every time about:memory "
+            "is refreshed.");
+    }
+
+    if (stringsNotableAboutMemoryMallocHeap > 0) {
+        MOZ_ASSERT(!zStats.isTotals);
+        REPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("strings/string(<about-memory>)/malloc-heap"),
+            KIND_HEAP, stringsNotableAboutMemoryMallocHeap,
+            "Non-inline string characters of strings that contain the "
+            "characters '" STRING_LENGTH "', which are probably from "
+            "about:memory itself. " MAYBE_OVERALLOCATED
+            " We filter them out rather than display them, because displaying "
+            "them would create even more such strings every time about:memory "
+            "is refreshed.");
+    }
+
+    if (sundriesGCHeap > 0) {
+        // We deliberately don't use ZCREPORT_GC_BYTES here.
+        REPORT_GC_BYTES(pathPrefix + NS_LITERAL_CSTRING("sundries/gc-heap"),
+            sundriesGCHeap,
+            "The sum of all 'gc-heap' measurements that are too small to be "
+            "worth showing individually.");
+    }
+
+    if (sundriesMallocHeap > 0) {
+        // We deliberately don't use ZCREPORT_BYTES here.
+        REPORT_BYTES(pathPrefix + NS_LITERAL_CSTRING("sundries/malloc-heap"),
+            KIND_HEAP, sundriesMallocHeap,
+            "The sum of all 'malloc-heap' measurements that are too small to "
+            "be worth showing individually.");
+    }
+
+    if (gcTotalOut)
+        *gcTotalOut += gcTotal;
+
+    return NS_OK;
+
+#   undef STRING_LENGTH
+}
+
+static nsresult
+ReportCompartmentStats(const JS::CompartmentStats &cStats,
+                       const xpc::CompartmentStatsExtras &extras,
+                       amIAddonManager *addonManager,
+                       nsIMemoryReporterCallback *cb,
+                       nsISupports *closure, size_t *gcTotalOut = nullptr)
+{
+    static const nsDependentCString addonPrefix("explicit/add-ons/");
+
+    size_t gcTotal = 0, sundriesGCHeap = 0, sundriesMallocHeap = 0;
+    nsAutoCString cJSPathPrefix = extras.jsPathPrefix;
+    nsAutoCString cDOMPathPrefix = extras.domPathPrefix;
+
+    // Only attempt to prefix if we got a location and the path wasn't already
+    // prefixed.
+    if (extras.location && addonManager &&
+        cJSPathPrefix.Find(addonPrefix, false, 0, 0) != 0) {
+        nsAutoCString addonId;
+        bool ok;
+        if (NS_SUCCEEDED(addonManager->MapURIToAddonID(extras.location,
+                                                        addonId, &ok))
+            && ok) {
+            // Insert the add-on id as "add-ons/@id@/" after "explicit/" to
+            // aggregate add-on compartments.
+            static const size_t explicitLength = strlen("explicit/");
+            addonId.Insert(NS_LITERAL_CSTRING("add-ons/"), 0);
+            addonId += "/";
+            cJSPathPrefix.Insert(addonId, explicitLength);
+            cDOMPathPrefix.Insert(addonId, explicitLength);
+        }
+    }
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/gc-heap/ordinary"),
+        cStats.objectsGCHeapOrdinary,
+        "Ordinary objects, i.e. not otherwise distinguished by memory "
+        "reporters.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/gc-heap/function"),
+        cStats.objectsGCHeapFunction,
+        "Function objects.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/gc-heap/dense-array"),
+        cStats.objectsGCHeapDenseArray,
+        "Dense array objects.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/gc-heap/slow-array"),
+        cStats.objectsGCHeapSlowArray,
+        "Slow array objects.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/gc-heap/cross-compartment-wrapper"),
+        cStats.objectsGCHeapCrossCompartmentWrapper,
+        "Cross-compartment wrapper objects.");
+
+    // Note that we use cDOMPathPrefix here.  This is because we measure orphan
+    // DOM nodes in the JS reporter, but we want to report them in a "dom"
+    // sub-tree rather than a "js" sub-tree.
+    ZCREPORT_BYTES(cDOMPathPrefix + NS_LITERAL_CSTRING("orphan-nodes"),
+        cStats.objectsPrivate,
+        "Orphan DOM nodes, i.e. those that are only reachable from JavaScript "
+        "objects.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/gc-heap/tree/global-parented"),
+        cStats.shapesGCHeapTreeGlobalParented,
+        "Shapes that (a) are in a property tree, and (b) represent an object "
+        "whose parent is the global object.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/gc-heap/tree/non-global-parented"),
+        cStats.shapesGCHeapTreeNonGlobalParented,
+        "Shapes that (a) are in a property tree, and (b) represent an object "
+        "whose parent is not the global object.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/gc-heap/dict"),
+        cStats.shapesGCHeapDict,
+        "Shapes that are in dictionary mode.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/gc-heap/base"),
+        cStats.shapesGCHeapBase,
+        "Base shapes, which collate data common to many shapes.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/malloc-heap/tree-tables"),
+        cStats.shapesMallocHeapTreeTables,
+        "Property tables belonging to shapes that are in a property tree.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/malloc-heap/dict-tables"),
+        cStats.shapesMallocHeapDictTables,
+        "Property tables that belong to shapes that are in dictionary mode.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/malloc-heap/tree-shape-kids"),
+        cStats.shapesMallocHeapTreeShapeKids,
+        "Kid hashes that belong to shapes that are in a property tree.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("shapes/malloc-heap/compartment-tables"),
+        cStats.shapesMallocHeapCompartmentTables,
+        "Compartment-wide tables storing shape information used during object "
+        "construction.");
+
+    ZCREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("scripts/gc-heap"),
+        cStats.scriptsGCHeap,
+        "JSScript instances. There is one per user-defined function in a "
+        "script, and one for the top-level code in a script.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("scripts/malloc-heap/data"),
+        cStats.scriptsMallocHeapData,
+        "Various variable-length tables in JSScripts.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("baseline/data"),
+        cStats.baselineData,
+        "The Baseline JIT's compilation data (BaselineScripts).");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("baseline/fallback-stubs"),
+        cStats.baselineStubsFallback,
+        "The Baseline JIT's fallback IC stubs (excluding code).");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("ion-data"),
+        cStats.ionData,
+        "The IonMonkey JIT's compilation data (IonScripts).");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("type-inference/type-scripts"),
+        cStats.typeInferenceTypeScripts,
+        "Type sets associated with scripts.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("type-inference/allocation-site-tables"),
+        cStats.typeInferenceAllocationSiteTables,
+        "Tables of type objects associated with allocation sites.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("type-inference/array-type-tables"),
+        cStats.typeInferenceArrayTypeTables,
+        "Tables of type objects associated with array literals.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("type-inference/object-type-tables"),
+        cStats.typeInferenceObjectTypeTables,
+        "Tables of type objects associated with object literals.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("compartment-object"),
+        cStats.compartmentObject,
+        "The JSCompartment object itself.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("cross-compartment-wrapper-table"),
+        cStats.crossCompartmentWrappersTable,
+        "The cross-compartment wrapper table.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("regexp-compartment"),
+        cStats.regexpCompartment,
+        "The regexp compartment.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("debuggees-set"),
+        cStats.debuggeesSet,
+        "The debuggees set.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/slots"),
+        cStats.objectsExtra.mallocHeapSlots,
+        "Non-fixed object slot arrays, which represent object properties.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/elements/non-asm.js"),
+        cStats.objectsExtra.mallocHeapElementsNonAsmJS,
+        "Non-asm.js indexed elements.");
+
+    // asm.js arrays are heap-allocated on some platforms and
+    // non-heap-allocated on others.  We never put them under sundries,
+    // because (a) in practice they're almost always larger than the sundries
+    // threshold, and (b) we'd need a third category of sundries ("non-heap"),
+    // which would be a pain.
+    size_t mallocHeapElementsAsmJS = cStats.objectsExtra.mallocHeapElementsAsmJS;
+    size_t nonHeapElementsAsmJS    = cStats.objectsExtra.nonHeapElementsAsmJS;
+    MOZ_ASSERT(mallocHeapElementsAsmJS == 0 || nonHeapElementsAsmJS == 0);
+    if (mallocHeapElementsAsmJS > 0) {
+        REPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/elements/asm.js"),
+            KIND_HEAP, mallocHeapElementsAsmJS,
+            "asm.js array buffer elements on the malloc heap.");
+    }
+    if (nonHeapElementsAsmJS > 0) {
+        REPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/non-heap/elements/asm.js"),
+            KIND_NONHEAP, nonHeapElementsAsmJS,
+            "asm.js array buffer elements outside both the malloc heap and "
+            "the GC heap.");
+    }
+
+    if (cStats.objectsExtra.nonHeapElementsMapped > 0) {
+        REPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/non-heap/elements/mapped"),
+            KIND_NONHEAP, cStats.objectsExtra.nonHeapElementsMapped,
+            "Memory-mapped array buffer elements.");
+    }
+
+    REPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/non-heap/code/asm.js"),
+        KIND_NONHEAP, cStats.objectsExtra.nonHeapCodeAsmJS,
+        "AOT-compiled asm.js code.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/asm.js-module-data"),
+        cStats.objectsExtra.mallocHeapAsmJSModuleData,
+        "asm.js module data.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/arguments-data"),
+        cStats.objectsExtra.mallocHeapArgumentsData,
+        "Data belonging to Arguments objects.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/regexp-statics"),
+        cStats.objectsExtra.mallocHeapRegExpStatics,
+        "Data belonging to the RegExpStatics object.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/property-iterator-data"),
+        cStats.objectsExtra.mallocHeapPropertyIteratorData,
+        "Data belonging to property iterator objects.");
+
+    ZCREPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("objects/malloc-heap/ctypes-data"),
+        cStats.objectsExtra.mallocHeapCtypesData,
+        "Data belonging to ctypes objects.");
+
+    if (sundriesGCHeap > 0) {
+        // We deliberately don't use ZCREPORT_GC_BYTES here.
+        REPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("sundries/gc-heap"),
+            sundriesGCHeap,
+            "The sum of all 'gc-heap' measurements that are too small to be "
+            "worth showing individually.");
+    }
+
+    if (sundriesMallocHeap > 0) {
+        // We deliberately don't use ZCREPORT_BYTES here.
+        REPORT_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("sundries/malloc-heap"),
+            KIND_HEAP, sundriesMallocHeap,
+            "The sum of all 'malloc-heap' measurements that are too small to "
+            "be worth showing individually.");
+    }
+
+    if (gcTotalOut)
+        *gcTotalOut += gcTotal;
+
+    return NS_OK;
+}
+
+static nsresult
+ReportScriptSourceStats(const ScriptSourceInfo &scriptSourceInfo,
+                        const nsACString &path,
+                        nsIHandleReportCallback *cb, nsISupports *closure,
+                        size_t &rtTotal)
+{
+    if (scriptSourceInfo.compressed > 0) {
+        RREPORT_BYTES(path + NS_LITERAL_CSTRING("compressed"),
+            KIND_HEAP, scriptSourceInfo.compressed,
+            "Compressed JavaScript source code.");
+    }
+
+    if (scriptSourceInfo.uncompressed > 0) {
+        RREPORT_BYTES(path + NS_LITERAL_CSTRING("uncompressed"),
+            KIND_HEAP, scriptSourceInfo.uncompressed,
+            "Uncompressed JavaScript source code.");
+    }
+
+    if (scriptSourceInfo.misc > 0) {
+        RREPORT_BYTES(path + NS_LITERAL_CSTRING("misc"),
+            KIND_HEAP, scriptSourceInfo.misc,
+            "Miscellaneous data relating to JavaScript source code.");
+    }
+
+    return NS_OK;
+}
+
+static nsresult
+ReportJSRuntimeExplicitTreeStats(const JS::RuntimeStats &rtStats,
+                                 const nsACString &rtPath,
+                                 amIAddonManager* addonManager,
+                                 nsIMemoryReporterCallback *cb,
+                                 nsISupports *closure, size_t *rtTotalOut)
+{
+    nsresult rv;
+
+    size_t gcTotal = 0;
+
+    for (size_t i = 0; i < rtStats.zoneStatsVector.length(); i++) {
+        const JS::ZoneStats &zStats = rtStats.zoneStatsVector[i];
+        const xpc::ZoneStatsExtras *extras =
+          static_cast<const xpc::ZoneStatsExtras*>(zStats.extra);
+        rv = ReportZoneStats(zStats, *extras, cb, closure, &gcTotal);
+        NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    for (size_t i = 0; i < rtStats.compartmentStatsVector.length(); i++) {
+        JS::CompartmentStats cStats = rtStats.compartmentStatsVector[i];
+        const xpc::CompartmentStatsExtras *extras =
+            static_cast<const xpc::CompartmentStatsExtras*>(cStats.extra);
+        rv = ReportCompartmentStats(cStats, *extras, addonManager, cb, closure,
+                                    &gcTotal);
+        NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    // Report the rtStats.runtime numbers under "runtime/", and compute their
+    // total for later.
+
+    size_t rtTotal = 0;
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/runtime-object"),
+        KIND_HEAP, rtStats.runtime.object,
+        "The JSRuntime object.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/atoms-table"),
+        KIND_HEAP, rtStats.runtime.atomsTable,
+        "The atoms table.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/contexts"),
+        KIND_HEAP, rtStats.runtime.contexts,
+        "JSContext objects and structures that belong to them.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/dtoa"),
+        KIND_HEAP, rtStats.runtime.dtoa,
+        "The DtoaState object, which is used for converting strings to "
+        "numbers and vice versa.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/temporary"),
+        KIND_HEAP, rtStats.runtime.temporary,
+        "Transient data (mostly parse nodes) held by the JSRuntime during "
+        "compilation.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/regexp-data"),
+        KIND_NONHEAP, rtStats.runtime.regexpData,
+        "Regexp JIT data.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/interpreter-stack"),
+        KIND_HEAP, rtStats.runtime.interpreterStack,
+        "JS interpreter frames.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/math-cache"),
+        KIND_HEAP, rtStats.runtime.mathCache,
+        "The math cache.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/source-data-cache"),
+        KIND_HEAP, rtStats.runtime.sourceDataCache,
+        "The source data cache, which holds decompressed script source code.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/script-data"),
+        KIND_HEAP, rtStats.runtime.scriptData,
+        "The table holding script data shared in the runtime.");
+
+    nsCString nonNotablePath =
+        rtPath + nsPrintfCString("runtime/script-sources/source(scripts=%d, <non-notable files>)/",
+                                 rtStats.runtime.scriptSourceInfo.numScripts);
+
+    rv = ReportScriptSourceStats(rtStats.runtime.scriptSourceInfo,
+                                 nonNotablePath, cb, closure, rtTotal);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    for (size_t i = 0; i < rtStats.runtime.notableScriptSources.length(); i++) {
+        const JS::NotableScriptSourceInfo& scriptSourceInfo =
+            rtStats.runtime.notableScriptSources[i];
+
+        // Escape / to \ before we put the filename into the memory reporter
+        // path, because we don't want any forward slashes in the string to
+        // count as path separators. Consumers of memory reporters (e.g.
+        // about:memory) will convert them back to / after doing path
+        // splitting.
+        nsDependentCString filename(scriptSourceInfo.filename_);
+        nsCString escapedFilename(filename);
+        escapedFilename.ReplaceSubstring("/", "\\");
+
+        nsCString notablePath = rtPath +
+            nsPrintfCString("runtime/script-sources/source(scripts=%d, %s)/",
+                            scriptSourceInfo.numScripts, escapedFilename.get());
+
+        rv = ReportScriptSourceStats(scriptSourceInfo, notablePath,
+                                     cb, closure, rtTotal);
+        NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/code/ion"),
+        KIND_NONHEAP, rtStats.runtime.code.ion,
+        "Code generated by the IonMonkey JIT.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/code/baseline"),
+        KIND_NONHEAP, rtStats.runtime.code.baseline,
+        "Code generated by the Baseline JIT.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/code/regexp"),
+        KIND_NONHEAP, rtStats.runtime.code.regexp,
+        "Code generated by the regexp JIT.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/code/other"),
+        KIND_NONHEAP, rtStats.runtime.code.other,
+        "Code generated by the JITs for wrappers and trampolines.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/code/unused"),
+        KIND_NONHEAP, rtStats.runtime.code.unused,
+        "Memory allocated by one of the JITs to hold code, but which is "
+        "currently unused.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/marker"),
+        KIND_HEAP, rtStats.runtime.gc.marker,
+        "The GC mark stack and gray roots.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/nursery-committed"),
+        KIND_NONHEAP, rtStats.runtime.gc.nurseryCommitted,
+        "Memory being used by the GC's nursery.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/nursery-huge-slots"),
+        KIND_NONHEAP, rtStats.runtime.gc.nurseryHugeSlots,
+        "Out-of-line slots and elements belonging to objects in the "
+        "nursery.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/vals"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferVals,
+        "Values in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/cells"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferCells,
+        "Cells in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/slots"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferSlots,
+        "Slots in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/whole-cells"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferWholeCells,
+        "Whole cells in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/reloc-vals"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferRelocVals,
+        "Relocatable values in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/reloc-cells"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferRelocCells,
+        "Relocatable cells in the store buffer.");
+
+    RREPORT_BYTES(rtPath + NS_LITERAL_CSTRING("runtime/gc/store-buffer/generics"),
+        KIND_HEAP, rtStats.runtime.gc.storeBufferGenerics,
+        "Generic things in the store buffer.");
+
+    if (rtTotalOut)
+        *rtTotalOut = rtTotal;
+
+    // Report GC numbers that don't belong to a compartment.
+
+    // We don't want to report decommitted memory in "explicit", so we just
+    // change the leading "explicit/" to "decommitted/".
+    nsCString rtPath2(rtPath);
+    rtPath2.Replace(0, strlen("explicit"), NS_LITERAL_CSTRING("decommitted"));
+    REPORT_GC_BYTES(rtPath2 + NS_LITERAL_CSTRING("gc-heap/decommitted-arenas"),
+        rtStats.gcHeapDecommittedArenas,
+        "GC arenas in non-empty chunks that is decommitted, i.e. it takes up "
+        "address space but no physical memory or swap space.");
+
+    REPORT_BYTES(rtPath2 + NS_LITERAL_CSTRING("runtime/gc/nursery-decommitted"),
+        KIND_NONHEAP, rtStats.runtime.gc.nurseryDecommitted,
+        "Memory allocated to the GC's nursery this is decommitted, i.e. it takes up "
+        "address space but no physical memory or swap space.");
+
+    REPORT_GC_BYTES(rtPath + NS_LITERAL_CSTRING("gc-heap/unused-chunks"),
+        rtStats.gcHeapUnusedChunks,
+        "Empty GC chunks which will soon be released unless claimed for new "
+        "allocations.");
+
+    REPORT_GC_BYTES(rtPath + NS_LITERAL_CSTRING("gc-heap/unused-arenas"),
+        rtStats.gcHeapUnusedArenas,
+        "Empty GC arenas within non-empty chunks.");
+
+    REPORT_GC_BYTES(rtPath + NS_LITERAL_CSTRING("gc-heap/chunk-admin"),
+        rtStats.gcHeapChunkAdmin,
+        "Bookkeeping information within GC chunks.");
+
+    // gcTotal is the sum of everything we've reported for the GC heap.  It
+    // should equal rtStats.gcHeapChunkTotal.
+    MOZ_ASSERT(gcTotal == rtStats.gcHeapChunkTotal);
+
+    return NS_OK;
+}
+
+nsresult
+ReportJSRuntimeExplicitTreeStats(const JS::RuntimeStats &rtStats,
+                                 const nsACString &rtPath,
+                                 nsIMemoryReporterCallback *cb,
+                                 nsISupports *closure, size_t *rtTotalOut)
+{
+    nsCOMPtr<amIAddonManager> am;
+    if (XRE_GetProcessType() == GeckoProcessType_Default) {
+        // Only try to access the service from the main process.
+        am = do_GetService("@mozilla.org/addons/integration;1");
+    }
+    return ReportJSRuntimeExplicitTreeStats(rtStats, rtPath, am.get(), cb,
+                                            closure, rtTotalOut);
+}
+
+
+} // namespace xpc
+
+class JSMainRuntimeCompartmentsReporter MOZ_FINAL : public nsIMemoryReporter
+{
+  public:
+    NS_DECL_ISUPPORTS
+
+    typedef js::Vector<nsCString, 0, js::SystemAllocPolicy> Paths;
+
+    static void CompartmentCallback(JSRuntime *rt, void* data, JSCompartment *c) {
+        // silently ignore OOM errors
+        Paths *paths = static_cast<Paths *>(data);
+        nsCString path;
+        GetCompartmentName(c, path, true);
+        path.Insert(js::IsSystemCompartment(c)
+                    ? NS_LITERAL_CSTRING("js-main-runtime-compartments/system/")
+                    : NS_LITERAL_CSTRING("js-main-runtime-compartments/user/"),
+                    0);
+        paths->append(path);
+    }
+
+    NS_IMETHOD CollectReports(nsIMemoryReporterCallback *cb,
+                              nsISupports *closure)
+    {
+        // First we collect the compartment paths.  Then we report them.  Doing
+        // the two steps interleaved is a bad idea, because calling |cb|
+        // from within CompartmentCallback() leads to all manner of assertions.
+
+        // Collect.
+
+        Paths paths;
+        JS_IterateCompartments(nsXPConnect::GetRuntimeInstance()->Runtime(),
+                               &paths, CompartmentCallback);
+
+        // Report.
+        for (size_t i = 0; i < paths.length(); i++)
+            // These ones don't need a description, hence the "".
+            REPORT(nsCString(paths[i]), KIND_OTHER, UNITS_COUNT, 1,
+                "A live compartment in the main JSRuntime.");
+
+        return NS_OK;
+    }
+};
+
+NS_IMPL_ISUPPORTS(JSMainRuntimeCompartmentsReporter, nsIMemoryReporter)
+
+MOZ_DEFINE_MALLOC_SIZE_OF(OrphanMallocSizeOf)
+
+namespace xpc {
+
+static size_t
+SizeOfTreeIncludingThis(nsINode *tree)
+{
+    size_t n = tree->SizeOfIncludingThis(OrphanMallocSizeOf);
+    for (nsIContent* child = tree->GetFirstChild(); child; child = child->GetNextNode(tree))
+        n += child->SizeOfIncludingThis(OrphanMallocSizeOf);
+
+    return n;
+}
+
+class OrphanReporter : public JS::ObjectPrivateVisitor
+{
+  public:
+    OrphanReporter(GetISupportsFun aGetISupports)
+      : JS::ObjectPrivateVisitor(aGetISupports)
+    {
+    }
+
+    virtual size_t sizeOfIncludingThis(nsISupports *aSupports) MOZ_OVERRIDE {
+        size_t n = 0;
+        nsCOMPtr<nsINode> node = do_QueryInterface(aSupports);
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=773533#c11 explains
+        // that we have to skip XBL elements because they violate certain
+        // assumptions.  Yuk.
+        if (node && !node->IsInDoc() &&
+            !(node->IsElement() && node->AsElement()->IsInNamespace(kNameSpaceID_XBL)))
+        {
+            // This is an orphan node.  If we haven't already handled the
+            // sub-tree that this node belongs to, measure the sub-tree's size
+            // and then record its root so we don't measure it again.
+            nsCOMPtr<nsINode> orphanTree = node->SubtreeRoot();
+            if (!mAlreadyMeasuredOrphanTrees.Contains(orphanTree)) {
+                n += SizeOfTreeIncludingThis(orphanTree);
+                mAlreadyMeasuredOrphanTrees.PutEntry(orphanTree);
+            }
+        }
+        return n;
+    }
+
+  private:
+    nsTHashtable <nsISupportsHashKey> mAlreadyMeasuredOrphanTrees;
+};
+
+#ifdef DEBUG
+static bool
+StartsWithExplicit(nsACString& s)
+{
+    const char* e = "explicit/";
+    return Substring(s, 0, strlen(e)).Equals(e);
+}
+#endif
+
+class XPCJSRuntimeStats : public JS::RuntimeStats
+{
+    WindowPaths *mWindowPaths;
+    WindowPaths *mTopWindowPaths;
+    bool mGetLocations;
+
+  public:
+    XPCJSRuntimeStats(WindowPaths *windowPaths, WindowPaths *topWindowPaths,
+                      bool getLocations)
+      : JS::RuntimeStats(JSMallocSizeOf),
+        mWindowPaths(windowPaths),
+        mTopWindowPaths(topWindowPaths),
+        mGetLocations(getLocations)
+    {}
+
+    ~XPCJSRuntimeStats() {
+        for (size_t i = 0; i != compartmentStatsVector.length(); ++i)
+            delete static_cast<xpc::CompartmentStatsExtras*>(compartmentStatsVector[i].extra);
+
+
+        for (size_t i = 0; i != zoneStatsVector.length(); ++i)
+            delete static_cast<xpc::ZoneStatsExtras*>(zoneStatsVector[i].extra);
+    }
+
+    virtual void initExtraZoneStats(JS::Zone *zone, JS::ZoneStats *zStats) MOZ_OVERRIDE {
+        // Get the compartment's global.
+        nsXPConnect *xpc = nsXPConnect::XPConnect();
+        AutoSafeJSContext cx;
+        JSCompartment *comp = js::GetAnyCompartmentInZone(zone);
+        xpc::ZoneStatsExtras *extras = new xpc::ZoneStatsExtras;
+        extras->pathPrefix.AssignLiteral("explicit/js-non-window/zones/");
+        RootedObject global(cx, JS_GetGlobalForCompartmentOrNull(cx, comp));
+        if (global) {
+            // Need to enter the compartment, otherwise GetNativeOfWrapper()
+            // might crash.
+            JSAutoCompartment ac(cx, global);
+            nsISupports *native = xpc->GetNativeOfWrapper(cx, global);
+            if (nsCOMPtr<nsPIDOMWindow> piwindow = do_QueryInterface(native)) {
+                // The global is a |window| object.  Use the path prefix that
+                // we should have already created for it.
+                if (mTopWindowPaths->Get(piwindow->WindowID(),
+                                         &extras->pathPrefix))
+                    extras->pathPrefix.AppendLiteral("/js-");
+            }
+        }
+
+        extras->pathPrefix += nsPrintfCString("zone(0x%p)/", (void *)zone);
+
+        MOZ_ASSERT(StartsWithExplicit(extras->pathPrefix));
+
+        zStats->extra = extras;
+    }
+
+    virtual void initExtraCompartmentStats(JSCompartment *c,
+                                           JS::CompartmentStats *cstats) MOZ_OVERRIDE
+    {
+        xpc::CompartmentStatsExtras *extras = new xpc::CompartmentStatsExtras;
+        nsCString cName;
+        GetCompartmentName(c, cName, true);
+        if (mGetLocations) {
+            CompartmentPrivate *cp = GetCompartmentPrivate(c);
+            if (cp)
+              cp->GetLocationURI(CompartmentPrivate::LocationHintAddon,
+                                 getter_AddRefs(extras->location));
+            // Note: cannot use amIAddonManager implementation at this point,
+            // as it is a JS service and the JS heap is currently not idle.
+            // Otherwise, we could have computed the add-on id at this point.
+        }
+
+        // Get the compartment's global.
+        nsXPConnect *xpc = nsXPConnect::XPConnect();
+        AutoSafeJSContext cx;
+        bool needZone = true;
+        RootedObject global(cx, JS_GetGlobalForCompartmentOrNull(cx, c));
+        if (global) {
+            // Need to enter the compartment, otherwise GetNativeOfWrapper()
+            // might crash.
+            JSAutoCompartment ac(cx, global);
+            nsISupports *native = xpc->GetNativeOfWrapper(cx, global);
+            if (nsCOMPtr<nsPIDOMWindow> piwindow = do_QueryInterface(native)) {
+                // The global is a |window| object.  Use the path prefix that
+                // we should have already created for it.
+                if (mWindowPaths->Get(piwindow->WindowID(),
+                                      &extras->jsPathPrefix)) {
+                    extras->domPathPrefix.Assign(extras->jsPathPrefix);
+                    extras->domPathPrefix.AppendLiteral("/dom/");
+                    extras->jsPathPrefix.AppendLiteral("/js-");
+                    needZone = false;
+                } else {
+                    extras->jsPathPrefix.AssignLiteral("explicit/js-non-window/zones/");
+                    extras->domPathPrefix.AssignLiteral("explicit/dom/unknown-window-global?!/");
+                }
+            } else {
+                extras->jsPathPrefix.AssignLiteral("explicit/js-non-window/zones/");
+                extras->domPathPrefix.AssignLiteral("explicit/dom/non-window-global?!/");
+            }
+        } else {
+            extras->jsPathPrefix.AssignLiteral("explicit/js-non-window/zones/");
+            extras->domPathPrefix.AssignLiteral("explicit/dom/no-global?!/");
+        }
+
+        if (needZone)
+            extras->jsPathPrefix += nsPrintfCString("zone(0x%p)/", (void *)js::GetCompartmentZone(c));
+
+        extras->jsPathPrefix += NS_LITERAL_CSTRING("compartment(") + cName + NS_LITERAL_CSTRING(")/");
+
+        // extras->jsPathPrefix is used for almost all the compartment-specific
+        // reports. At this point it has the form
+        // "<something>compartment(<cname>)/".
+        //
+        // extras->domPathPrefix is used for DOM orphan nodes, which are
+        // counted by the JS reporter but reported as part of the DOM
+        // measurements. At this point it has the form "<something>/dom/" if
+        // this compartment belongs to an nsGlobalWindow, and
+        // "explicit/dom/<something>?!/" otherwise (in which case it shouldn't
+        // be used, because non-nsGlobalWindow compartments shouldn't have
+        // orphan DOM nodes).
+
+        MOZ_ASSERT(StartsWithExplicit(extras->jsPathPrefix));
+        MOZ_ASSERT(StartsWithExplicit(extras->domPathPrefix));
+
+        cstats->extra = extras;
+    }
+};
+
+nsresult
+JSReporter::CollectReports(WindowPaths *windowPaths,
+                           WindowPaths *topWindowPaths,
+                           nsIMemoryReporterCallback *cb,
+                           nsISupports *closure)
+{
+    XPCJSRuntime *xpcrt = nsXPConnect::GetRuntimeInstance();
+
+    // In the first step we get all the stats and stash them in a local
+    // data structure.  In the second step we pass all the stashed stats to
+    // the callback.  Separating these steps is important because the
+    // callback may be a JS function, and executing JS while getting these
+    // stats seems like a bad idea.
+
+    nsCOMPtr<amIAddonManager> addonManager;
+    if (XRE_GetProcessType() == GeckoProcessType_Default) {
+        // Only try to access the service from the main process.
+        addonManager = do_GetService("@mozilla.org/addons/integration;1");
+    }
+    bool getLocations = !!addonManager;
+    XPCJSRuntimeStats rtStats(windowPaths, topWindowPaths, getLocations);
+    OrphanReporter orphanReporter(XPCConvert::GetISupportsFromJSObject);
+    if (!JS::CollectRuntimeStats(xpcrt->Runtime(), &rtStats, &orphanReporter))
+        return NS_ERROR_FAILURE;
+
+    size_t xpconnect = xpcrt->SizeOfIncludingThis(JSMallocSizeOf);
+
+    XPCWrappedNativeScope::ScopeSizeInfo sizeInfo(JSMallocSizeOf);
+    XPCWrappedNativeScope::AddSizeOfAllScopesIncludingThis(&sizeInfo);
+
+    mozJSComponentLoader* loader = mozJSComponentLoader::Get();
+    size_t jsComponentLoaderSize = loader ? loader->SizeOfIncludingThis(JSMallocSizeOf) : 0;
+
+    // This is the second step (see above).  First we report stuff in the
+    // "explicit" tree, then we report other stuff.
+
+    nsresult rv;
+    size_t rtTotal = 0;
+    rv = xpc::ReportJSRuntimeExplicitTreeStats(rtStats,
+                                               NS_LITERAL_CSTRING("explicit/js-non-window/"),
+                                               addonManager, cb, closure,
+                                               &rtTotal);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Report the sums of the compartment numbers.
+    xpc::CompartmentStatsExtras cExtrasTotal;
+    cExtrasTotal.jsPathPrefix.AssignLiteral("js-main-runtime/compartments/");
+    cExtrasTotal.domPathPrefix.AssignLiteral("window-objects/dom/");
+    rv = ReportCompartmentStats(rtStats.cTotals, cExtrasTotal, addonManager,
+                                cb, closure);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    xpc::ZoneStatsExtras zExtrasTotal;
+    zExtrasTotal.pathPrefix.AssignLiteral("js-main-runtime/zones/");
+    rv = ReportZoneStats(rtStats.zTotals, zExtrasTotal, cb, closure);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Report the sum of the runtime/ numbers.
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime/runtime"),
+        KIND_OTHER, rtTotal,
+        "The sum of all measurements under 'explicit/js-non-window/runtime/'.");
+
+    // Report the numbers for memory outside of compartments.
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime/gc-heap/unused-chunks"),
+        KIND_OTHER, rtStats.gcHeapUnusedChunks,
+        "The same as 'explicit/js-non-window/gc-heap/unused-chunks'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime/gc-heap/unused-arenas"),
+        KIND_OTHER, rtStats.gcHeapUnusedArenas,
+        "The same as 'explicit/js-non-window/gc-heap/unused-arenas'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime/gc-heap/chunk-admin"),
+        KIND_OTHER, rtStats.gcHeapChunkAdmin,
+        "The same as 'explicit/js-non-window/gc-heap/chunk-admin'.");
+
+    // Report a breakdown of the committed GC space.
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/unused/chunks"),
+        KIND_OTHER, rtStats.gcHeapUnusedChunks,
+        "The same as 'explicit/js-non-window/gc-heap/unused-chunks'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/unused/arenas"),
+        KIND_OTHER, rtStats.gcHeapUnusedArenas,
+        "The same as 'explicit/js-non-window/gc-heap/unused-arenas'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/unused/gc-things"),
+        KIND_OTHER, rtStats.zTotals.unusedGCThings,
+        "The same as 'js-main-runtime/zones/unused-gc-things'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/used/chunk-admin"),
+        KIND_OTHER, rtStats.gcHeapChunkAdmin,
+        "The same as 'explicit/js-non-window/gc-heap/chunk-admin'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/used/arena-admin"),
+        KIND_OTHER, rtStats.zTotals.gcHeapArenaAdmin,
+        "The same as 'js-main-runtime/zones/gc-heap-arena-admin'.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("js-main-runtime-gc-heap-committed/used/gc-things"),
+        KIND_OTHER, rtStats.gcHeapGCThings,
+        "GC things: objects, strings, scripts, etc.");
+
+    // Report xpconnect.
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("explicit/xpconnect/runtime"),
+        KIND_HEAP, xpconnect,
+        "The XPConnect runtime.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("explicit/xpconnect/scopes"),
+        KIND_HEAP, sizeInfo.mScopeAndMapSize,
+        "XPConnect scopes.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("explicit/xpconnect/proto-iface-cache"),
+        KIND_HEAP, sizeInfo.mProtoAndIfaceCacheSize,
+        "Prototype and interface binding caches.");
+
+    REPORT_BYTES(NS_LITERAL_CSTRING("explicit/xpconnect/js-component-loader"),
+        KIND_HEAP, jsComponentLoaderSize,
+        "XPConnect's JS component loader.");
+
+    return NS_OK;
+}
+
+static nsresult
+JSSizeOfTab(JSObject *objArg, size_t *jsObjectsSize, size_t *jsStringsSize,
+            size_t *jsPrivateSize, size_t *jsOtherSize)
+{
+    JSRuntime *rt = nsXPConnect::GetRuntimeInstance()->Runtime();
+    JS::RootedObject obj(rt, objArg);
+
+    TabSizes sizes;
+    OrphanReporter orphanReporter(XPCConvert::GetISupportsFromJSObject);
+    NS_ENSURE_TRUE(JS::AddSizeOfTab(rt, obj, moz_malloc_size_of,
+                                    &orphanReporter, &sizes),
+                   NS_ERROR_OUT_OF_MEMORY);
+
+    *jsObjectsSize = sizes.objects;
+    *jsStringsSize = sizes.strings;
+    *jsPrivateSize = sizes.private_;
+    *jsOtherSize   = sizes.other;
+    return NS_OK;
+}
+
+} // namespace xpc
+
+#ifdef MOZ_CRASHREPORTER
+static bool
+DiagnosticMemoryCallback(void *ptr, size_t size)
+{
+    return CrashReporter::RegisterAppMemory(ptr, size) == NS_OK;
+}
+#endif
+
+static void
+AccumulateTelemetryCallback(int id, uint32_t sample)
+{
+    switch (id) {
+      case JS_TELEMETRY_GC_REASON:
+        Telemetry::Accumulate(Telemetry::GC_REASON_2, sample);
+        break;
+      case JS_TELEMETRY_GC_IS_COMPARTMENTAL:
+        Telemetry::Accumulate(Telemetry::GC_IS_COMPARTMENTAL, sample);
+        break;
+      case JS_TELEMETRY_GC_MS:
+        Telemetry::Accumulate(Telemetry::GC_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_MAX_PAUSE_MS:
+        Telemetry::Accumulate(Telemetry::GC_MAX_PAUSE_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_MARK_MS:
+        Telemetry::Accumulate(Telemetry::GC_MARK_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_SWEEP_MS:
+        Telemetry::Accumulate(Telemetry::GC_SWEEP_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_MARK_ROOTS_MS:
+        Telemetry::Accumulate(Telemetry::GC_MARK_ROOTS_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_MARK_GRAY_MS:
+        Telemetry::Accumulate(Telemetry::GC_MARK_GRAY_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_SLICE_MS:
+        Telemetry::Accumulate(Telemetry::GC_SLICE_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_MMU_50:
+        Telemetry::Accumulate(Telemetry::GC_MMU_50, sample);
+        break;
+      case JS_TELEMETRY_GC_RESET:
+        Telemetry::Accumulate(Telemetry::GC_RESET, sample);
+        break;
+      case JS_TELEMETRY_GC_INCREMENTAL_DISABLED:
+        Telemetry::Accumulate(Telemetry::GC_INCREMENTAL_DISABLED, sample);
+        break;
+      case JS_TELEMETRY_GC_NON_INCREMENTAL:
+        Telemetry::Accumulate(Telemetry::GC_NON_INCREMENTAL, sample);
+        break;
+      case JS_TELEMETRY_GC_SCC_SWEEP_TOTAL_MS:
+        Telemetry::Accumulate(Telemetry::GC_SCC_SWEEP_TOTAL_MS, sample);
+        break;
+      case JS_TELEMETRY_GC_SCC_SWEEP_MAX_PAUSE_MS:
+        Telemetry::Accumulate(Telemetry::GC_SCC_SWEEP_MAX_PAUSE_MS, sample);
+        break;
+    }
+}
+
+static void
+CompartmentNameCallback(JSRuntime *rt, JSCompartment *comp,
+                        char *buf, size_t bufsize)
+{
+    nsCString name;
+    GetCompartmentName(comp, name, false);
+    if (name.Length() >= bufsize)
+        name.Truncate(bufsize - 1);
+    memcpy(buf, name.get(), name.Length() + 1);
+}
+
+static bool
+PreserveWrapper(JSContext *cx, JSObject *obj)
+{
+    MOZ_ASSERT(cx);
+    MOZ_ASSERT(obj);
+    MOZ_ASSERT(IS_WN_REFLECTOR(obj) || mozilla::dom::IsDOMObject(obj));
+
+    return mozilla::dom::IsDOMObject(obj) && mozilla::dom::TryPreserveWrapper(obj);
+}
+
+static nsresult
+ReadSourceFromFilename(JSContext *cx, const char *filename, jschar **src, size_t *len)
+{
+    nsresult rv;
+
+    // mozJSSubScriptLoader prefixes the filenames of the scripts it loads with
+    // the filename of its caller. Axe that if present.
+    const char *arrow;
+    while ((arrow = strstr(filename, " -> ")))
+        filename = arrow + strlen(" -> ");
+
+    // Get the URI.
+    nsCOMPtr<nsIURI> uri;
+    rv = NS_NewURI(getter_AddRefs(uri), filename);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIChannel> scriptChannel;
+    rv = NS_NewChannel(getter_AddRefs(scriptChannel), uri);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Only allow local reading.
+    nsCOMPtr<nsIURI> actualUri;
+    rv = scriptChannel->GetURI(getter_AddRefs(actualUri));
+    NS_ENSURE_SUCCESS(rv, rv);
+    nsCString scheme;
+    rv = actualUri->GetScheme(scheme);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!scheme.EqualsLiteral("file") && !scheme.EqualsLiteral("jar"))
+        return NS_OK;
+
+    nsCOMPtr<nsIInputStream> scriptStream;
+    rv = scriptChannel->Open(getter_AddRefs(scriptStream));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    uint64_t rawLen;
+    rv = scriptStream->Available(&rawLen);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!rawLen)
+        return NS_ERROR_FAILURE;
+
+    // Technically, this should be SIZE_MAX, but we don't run on machines
+    // where that would be less than UINT32_MAX, and the latter is already
+    // well beyond a reasonable limit.
+    if (rawLen > UINT32_MAX)
+        return NS_ERROR_FILE_TOO_BIG;
+
+    // Allocate an internal buf the size of the file.
+    nsAutoArrayPtr<unsigned char> buf(new unsigned char[rawLen]);
+    if (!buf)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    unsigned char *ptr = buf, *end = ptr + rawLen;
+    while (ptr < end) {
+        uint32_t bytesRead;
+        rv = scriptStream->Read(reinterpret_cast<char *>(ptr), end - ptr, &bytesRead);
+        if (NS_FAILED(rv))
+            return rv;
+        MOZ_ASSERT(bytesRead > 0, "stream promised more bytes before EOF");
+        ptr += bytesRead;
+    }
+
+    rv = nsScriptLoader::ConvertToUTF16(scriptChannel, buf, rawLen, EmptyString(),
+                                        nullptr, *src, *len);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (!*src)
+        return NS_ERROR_FAILURE;
+
+    // Historically this method used JS_malloc() which updates the GC memory
+    // accounting.  Since ConvertToUTF16() now uses js_malloc() instead we
+    // update the accounting manually after the fact.
+    JS_updateMallocCounter(cx, *len);
+
+    return NS_OK;
+}
+
+// The JS engine calls this object's 'load' member function when it needs
+// the source for a chrome JS function. See the comment in the XPCJSRuntime
+// constructor.
+class XPCJSSourceHook: public js::SourceHook {
+    bool load(JSContext *cx, const char *filename, jschar **src, size_t *length) {
+        *src = nullptr;
+        *length = 0;
+
+        if (!nsContentUtils::IsCallerChrome())
+            return true;
+
+        if (!filename)
+            return true;
+
+        nsresult rv = ReadSourceFromFilename(cx, filename, src, length);
+        if (NS_FAILED(rv)) {
+            xpc::Throw(cx, rv);
+            return false;
+        }
+
+        return true;
+    }
+};
+
+static const JSWrapObjectCallbacks WrapObjectCallbacks = {
+    xpc::WrapperFactory::Rewrap,
+    xpc::WrapperFactory::PrepareForWrapping
+};
+
+XPCJSRuntime::XPCJSRuntime(nsXPConnect* aXPConnect)
+   : CycleCollectedJSRuntime(nullptr, 32L * 1024L * 1024L, JS_USE_HELPER_THREADS),
+   mJSContextStack(new XPCJSContextStack(MOZ_THIS_IN_INITIALIZER_LIST())),
+   mCallContext(nullptr),
+   mAutoRoots(nullptr),
+   mResolveName(JSID_VOID),
+   mResolvingWrapper(nullptr),
+   mWrappedJSMap(JSObject2WrappedJSMap::newMap(XPC_JS_MAP_SIZE)),
+   mWrappedJSClassMap(IID2WrappedJSClassMap::newMap(XPC_JS_CLASS_MAP_SIZE)),
+   mIID2NativeInterfaceMap(IID2NativeInterfaceMap::newMap(XPC_NATIVE_INTERFACE_MAP_SIZE)),
+   mClassInfo2NativeSetMap(ClassInfo2NativeSetMap::newMap(XPC_NATIVE_SET_MAP_SIZE)),
+   mNativeSetMap(NativeSetMap::newMap(XPC_NATIVE_SET_MAP_SIZE)),
+   mThisTranslatorMap(IID2ThisTranslatorMap::newMap(XPC_THIS_TRANSLATOR_MAP_SIZE)),
+   mNativeScriptableSharedMap(XPCNativeScriptableSharedMap::newMap(XPC_NATIVE_JSCLASS_MAP_SIZE)),
+   mDyingWrappedNativeProtoMap(XPCWrappedNativeProtoMap::newMap(XPC_DYING_NATIVE_PROTO_MAP_SIZE)),
+   mDetachedWrappedNativeProtoMap(XPCWrappedNativeProtoMap::newMap(XPC_DETACHED_NATIVE_PROTO_MAP_SIZE)),
+   mGCIsRunning(false),
+   mWrappedJSToReleaseArray(),
+   mNativesToReleaseArray(),
+   mDoingFinalization(false),
+   mVariantRoots(nullptr),
+   mWrappedJSRoots(nullptr),
+   mObjectHolderRoots(nullptr),
+   mWatchdogManager(new WatchdogManager(MOZ_THIS_IN_INITIALIZER_LIST())),
+   mJunkScope(MOZ_THIS_IN_INITIALIZER_LIST()->Runtime(), nullptr),
+   mCompilationScope(MOZ_THIS_IN_INITIALIZER_LIST()->Runtime(), nullptr),
+   mAsyncSnowWhiteFreer(new AsyncFreeSnowWhite())
+{
+    DOM_InitInterfaces();
+
+    // these jsids filled in later when we have a JSContext to work with.
+    mStrIDs[0] = JSID_VOID;
+
+    MOZ_ASSERT(Runtime());
+    JSRuntime* runtime = Runtime();
+
+    auto rtPrivate = new PerThreadAtomCache();
+    memset(rtPrivate, 0, sizeof(PerThreadAtomCache));
+    JS_SetRuntimePrivate(runtime, rtPrivate);
+
+    // Unconstrain the runtime's threshold on nominal heap size, to avoid
+    // triggering GC too often if operating continuously near an arbitrary
+    // finite threshold (0xffffffff is infinity for uint32_t parameters).
+    // This leaves the maximum-JS_malloc-bytes threshold still in effect
+    // to cause period, and we hope hygienic, last-ditch GCs from within
+    // the GC's allocator.
+    JS_SetGCParameter(runtime, JSGC_MAX_BYTES, 0xffffffff);
+
+    // The JS engine permits us to set different stack limits for system code,
+    // trusted script, and untrusted script. We have tests that ensure that
+    // we can always execute 10 "heavy" (eval+with) stack frames deeper in
+    // privileged code. Our stack sizes vary greatly in different configurations,
+    // so satisfying those tests requires some care. Manual measurements of the
+    // number of heavy stack frames achievable gives us the following rough data,
+    // ordered by the effective categories in which they are grouped in the
+    // JS_SetNativeStackQuota call (which predates this analysis).
+    //
+    // (NB: These numbers may have drifted recently - see bug 938429)
+    // OSX 64-bit Debug: 7MB stack, 636 stack frames => ~11.3k per stack frame
+    // OSX64 Opt: 7MB stack, 2440 stack frames => ~3k per stack frame
+    //
+    // Linux 32-bit Debug: 2MB stack, 447 stack frames => ~4.6k per stack frame
+    // Linux 64-bit Debug: 4MB stack, 501 stack frames => ~8.2k per stack frame
+    //
+    // Windows (Opt+Debug): 900K stack, 235 stack frames => ~3.4k per stack frame
+    //
+    // Linux 32-bit Opt: 1MB stack, 272 stack frames => ~3.8k per stack frame
+    // Linux 64-bit Opt: 2MB stack, 316 stack frames => ~6.5k per stack frame
+    //
+    // We tune the trusted/untrusted quotas for each configuration to achieve our
+    // invariants while attempting to minimize overhead. In contrast, our buffer
+    // between system code and trusted script is a very unscientific 10k.
+    const size_t kSystemCodeBuffer = 10 * 1024;
+
+    // Our "default" stack is what we use in configurations where we don't have
+    // a compelling reason to do things differently. This is effectively 1MB on
+    // 32-bit platforms and 2MB on 64-bit platforms.
+    const size_t kDefaultStackQuota = 128 * sizeof(size_t) * 1024;
+
+    // Set stack sizes for different configurations. It's probably not great for
+    // the web to base this decision primarily on the default stack size that the
+    // underlying platform makes available, but that seems to be what we do. :-(
+
+#if defined(XP_MACOSX) || defined(DARWIN)
+    // MacOS has a gargantuan default stack size of 8MB. Go wild with 7MB,
+    // and give trusted script 140k extra. The stack is huge on mac anyway.
+    const size_t kStackQuota = 7 * 1024 * 1024;
+    const size_t kTrustedScriptBuffer = 140 * 1024;
+#elif defined(MOZ_ASAN)
+    // ASan requires more stack space due to red-zones, so give it double the
+    // default (2MB on 32-bit, 4MB on 64-bit). ASAN stack frame measurements
+    // were not taken at the time of this writing, so we hazard a guess that
+    // ASAN builds have roughly thrice the stack overhead as normal builds.
+    // On normal builds, the largest stack frame size we might encounter is
+    // 8.2k, so let's use a buffer of 8.2 * 3 * 10 = 246k.
+    const size_t kStackQuota =  2 * kDefaultStackQuota;
+    const size_t kTrustedScriptBuffer = 246 * 1024;
+#elif defined(XP_WIN)
+    // 1MB is the default stack size on Windows, so the default 1MB stack quota
+    // we'd get on win32 is slightly too large. Use 900k instead. And since
+    // windows stack frames are 3.4k each, let's use a buffer of 50k.
+    const size_t kStackQuota = 900 * 1024;
+    const size_t kTrustedScriptBuffer = 50 * 1024;
+    // The following two configurations are linux-only. Given the numbers above,
+    // we use 50k and 100k trusted buffers on 32-bit and 64-bit respectively.
+#elif defined(DEBUG)
+    // Bug 803182: account for the 4x difference in the size of js::Interpret
+    // between optimized and debug builds.
+    // XXXbholley - Then why do we only account for 2x of difference?
+    const size_t kStackQuota = 2 * kDefaultStackQuota;
+    const size_t kTrustedScriptBuffer = sizeof(size_t) * 12800;
+#else
+    const size_t kStackQuota = kDefaultStackQuota;
+    const size_t kTrustedScriptBuffer = sizeof(size_t) * 12800;
+#endif
+
+    // Avoid an unused variable warning on platforms where we don't use the
+    // default.
+    (void) kDefaultStackQuota;
+
+    JS_SetNativeStackQuota(runtime,
+                           kStackQuota,
+                           kStackQuota - kSystemCodeBuffer,
+                           kStackQuota - kSystemCodeBuffer - kTrustedScriptBuffer);
+
+    JS_SetDestroyCompartmentCallback(runtime, CompartmentDestroyedCallback);
+    JS_SetCompartmentNameCallback(runtime, CompartmentNameCallback);
+    mPrevGCSliceCallback = JS::SetGCSliceCallback(runtime, GCSliceCallback);
+    JS_SetFinalizeCallback(runtime, FinalizeCallback);
+    JS_SetWrapObjectCallbacks(runtime, &WrapObjectCallbacks);
+    js::SetPreserveWrapperCallback(runtime, PreserveWrapper);
+#ifdef MOZ_CRASHREPORTER
+    JS_EnumerateDiagnosticMemoryRegions(DiagnosticMemoryCallback);
+#endif
+#ifdef MOZ_ENABLE_PROFILER_SPS
+    if (PseudoStack *stack = mozilla_get_pseudo_stack())
+        stack->sampleRuntime(runtime);
+#endif
+    JS_SetAccumulateTelemetryCallback(runtime, AccumulateTelemetryCallback);
+    js::SetDefaultJSContextCallback(runtime, DefaultJSContextCallback);
+    js::SetActivityCallback(runtime, ActivityCallback, this);
+    js::SetCTypesActivityCallback(runtime, CTypesActivityCallback);
+    JS_SetInterruptCallback(runtime, InterruptCallback);
+    JS::SetOutOfMemoryCallback(runtime, OutOfMemoryCallback);
+
+    // The JS engine needs to keep the source code around in order to implement
+    // Function.prototype.toSource(). It'd be nice to not have to do this for
+    // chrome code and simply stub out requests for source on it. Life is not so
+    // easy, unfortunately. Nobody relies on chrome toSource() working in core
+    // browser code, but chrome tests use it. The worst offenders are addons,
+    // which like to monkeypatch chrome functions by calling toSource() on them
+    // and using regular expressions to modify them. We avoid keeping most browser
+    // JS source code in memory by setting LAZY_SOURCE on JS::CompileOptions when
+    // compiling some chrome code. This causes the JS engine not save the source
+    // code in memory. When the JS engine is asked to provide the source for a
+    // function compiled with LAZY_SOURCE, it calls SourceHook to load it.
+    ///
+    // Note we do have to retain the source code in memory for scripts compiled in
+    // compileAndGo mode and compiled function bodies (from
+    // JS_CompileFunction*). In practice, this means content scripts and event
+    // handlers.
+    js::SetSourceHook(runtime, new XPCJSSourceHook);
+
+    // Set up locale information and callbacks for the newly-created runtime so
+    // that the various toLocaleString() methods, localeCompare(), and other
+    // internationalization APIs work as desired.
+    if (!xpc_LocalizeRuntime(runtime))
+        NS_RUNTIMEABORT("xpc_LocalizeRuntime failed.");
+
+    // Register memory reporters and distinguished amount functions.
+    RegisterStrongMemoryReporter(new JSMainRuntimeCompartmentsReporter());
+    RegisterStrongMemoryReporter(new JSMainRuntimeTemporaryPeakReporter());
+    RegisterJSMainRuntimeGCHeapDistinguishedAmount(JSMainRuntimeGCHeapDistinguishedAmount);
+    RegisterJSMainRuntimeTemporaryPeakDistinguishedAmount(JSMainRuntimeTemporaryPeakDistinguishedAmount);
+    RegisterJSMainRuntimeCompartmentsSystemDistinguishedAmount(JSMainRuntimeCompartmentsSystemDistinguishedAmount);
+    RegisterJSMainRuntimeCompartmentsUserDistinguishedAmount(JSMainRuntimeCompartmentsUserDistinguishedAmount);
+    mozilla::RegisterJSSizeOfTab(JSSizeOfTab);
+
+    // Install a JavaScript 'debugger' keyword handler in debug builds only
+#ifdef DEBUG
+    if (!JS_GetGlobalDebugHooks(runtime)->debuggerHandler)
+        xpc_InstallJSDebuggerKeywordHandler(runtime);
+#endif
+
+    // Watch for the JS boolean options.
+    ReloadPrefsCallback(nullptr, this);
+    Preferences::RegisterCallback(ReloadPrefsCallback, JS_OPTIONS_DOT_STR, this);
+}
+
+// static
+XPCJSRuntime*
+XPCJSRuntime::newXPCJSRuntime(nsXPConnect* aXPConnect)
+{
+    NS_PRECONDITION(aXPConnect,"bad param");
+
+    XPCJSRuntime* self = new XPCJSRuntime(aXPConnect);
+
+    if (self                                    &&
+        self->Runtime()                         &&
+        self->GetWrappedJSMap()                 &&
+        self->GetWrappedJSClassMap()            &&
+        self->GetIID2NativeInterfaceMap()       &&
+        self->GetClassInfo2NativeSetMap()       &&
+        self->GetNativeSetMap()                 &&
+        self->GetThisTranslatorMap()            &&
+        self->GetNativeScriptableSharedMap()    &&
+        self->GetDyingWrappedNativeProtoMap()   &&
+        self->mWatchdogManager) {
+        return self;
+    }
+
+    NS_RUNTIMEABORT("new XPCJSRuntime failed to initialize.");
+
+    delete self;
+    return nullptr;
+}
+
+bool
+XPCJSRuntime::OnJSContextNew(JSContext *cx)
+{
+    // If we were the first cx ever created (like the SafeJSContext), the caller
+    // would have had no way to enter a request. Enter one now before doing the
+    // rest of the cx setup.
+    JSAutoRequest ar(cx);
+
+    // if it is our first context then we need to generate our string ids
+    if (JSID_IS_VOID(mStrIDs[0])) {
+        RootedString str(cx);
+        for (unsigned i = 0; i < IDX_TOTAL_COUNT; i++) {
+            str = JS_InternString(cx, mStrings[i]);
+            if (!str) {
+                mStrIDs[0] = JSID_VOID;
+                return false;
+            }
+            mStrIDs[i] = INTERNED_STRING_TO_JSID(cx, str);
+            mStrJSVals[i] = STRING_TO_JSVAL(str);
+        }
+
+        if (!mozilla::dom::DefineStaticJSVals(cx)) {
+            return false;
+        }
+    }
+
+    XPCContext* xpc = new XPCContext(this, cx);
+    if (!xpc)
+        return false;
+
+    return true;
+}
+
+bool
+XPCJSRuntime::DescribeCustomObjects(JSObject* obj, const js::Class* clasp,
+                                    char (&name)[72]) const
+{
+    XPCNativeScriptableInfo *si = nullptr;
+
+    if (!IS_PROTO_CLASS(clasp)) {
+        return false;
+    }
+
+    XPCWrappedNativeProto *p =
+        static_cast<XPCWrappedNativeProto*>(xpc_GetJSPrivate(obj));
+    si = p->GetScriptableInfo();
+    
+    if (!si) {
+        return false;
+    }
+
+    JS_snprintf(name, sizeof(name), "JS Object (%s - %s)",
+                clasp->name, si->GetJSClass()->name);
+    return true;
+}
+
+bool
+XPCJSRuntime::NoteCustomGCThingXPCOMChildren(const js::Class* clasp, JSObject* obj,
+                                             nsCycleCollectionTraversalCallback& cb) const
+{
+    if (clasp != &XPC_WN_Tearoff_JSClass) {
+        return false;
+    }
+
+    // A tearoff holds a strong reference to its native object
+    // (see XPCWrappedNative::FlatJSObjectFinalized). Its XPCWrappedNative
+    // will be held alive through the parent of the JSObject of the tearoff.
+    XPCWrappedNativeTearOff *to =
+        static_cast<XPCWrappedNativeTearOff*>(xpc_GetJSPrivate(obj));
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "xpc_GetJSPrivate(obj)->mNative");
+    cb.NoteXPCOMChild(to->GetNative());
+    return true;
+}
+
+/***************************************************************************/
+
+#ifdef DEBUG
+static PLDHashOperator
+WrappedJSClassMapDumpEnumerator(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                                uint32_t number, void *arg)
+{
+    ((IID2WrappedJSClassMap::Entry*)hdr)->value->DebugDump(*(int16_t*)arg);
+    return PL_DHASH_NEXT;
+}
+static PLDHashOperator
+NativeSetDumpEnumerator(PLDHashTable *table, PLDHashEntryHdr *hdr,
+                        uint32_t number, void *arg)
+{
+    ((NativeSetMap::Entry*)hdr)->key_value->DebugDump(*(int16_t*)arg);
+    return PL_DHASH_NEXT;
+}
+#endif
+
+void
+XPCJSRuntime::DebugDump(int16_t depth)
+{
+#ifdef DEBUG
+    depth--;
+    XPC_LOG_ALWAYS(("XPCJSRuntime @ %x", this));
+        XPC_LOG_INDENT();
+        XPC_LOG_ALWAYS(("mJSRuntime @ %x", Runtime()));
+
+        XPC_LOG_ALWAYS(("mWrappedJSToReleaseArray @ %x with %d wrappers(s)", \
+                        &mWrappedJSToReleaseArray,
+                        mWrappedJSToReleaseArray.Length()));
+
+        int cxCount = 0;
+        JSContext* iter = nullptr;
+        while (JS_ContextIterator(Runtime(), &iter))
+            ++cxCount;
+        XPC_LOG_ALWAYS(("%d JS context(s)", cxCount));
+
+        iter = nullptr;
+        while (JS_ContextIterator(Runtime(), &iter)) {
+            XPCContext *xpc = XPCContext::GetXPCContext(iter);
+            XPC_LOG_INDENT();
+            xpc->DebugDump(depth);
+            XPC_LOG_OUTDENT();
+        }
+
+        XPC_LOG_ALWAYS(("mWrappedJSClassMap @ %x with %d wrapperclasses(s)",  \
+                        mWrappedJSClassMap, mWrappedJSClassMap ?              \
+                        mWrappedJSClassMap->Count() : 0));
+        // iterate wrappersclasses...
+        if (depth && mWrappedJSClassMap && mWrappedJSClassMap->Count()) {
+            XPC_LOG_INDENT();
+            mWrappedJSClassMap->Enumerate(WrappedJSClassMapDumpEnumerator, &depth);
+            XPC_LOG_OUTDENT();
+        }
+        XPC_LOG_ALWAYS(("mWrappedJSMap @ %x with %d wrappers(s)",             \
+                        mWrappedJSMap, mWrappedJSMap ?                        \
+                        mWrappedJSMap->Count() : 0));
+        // iterate wrappers...
+        if (depth && mWrappedJSMap && mWrappedJSMap->Count()) {
+            XPC_LOG_INDENT();
+            mWrappedJSMap->Dump(depth);
+            XPC_LOG_OUTDENT();
+        }
+
+        XPC_LOG_ALWAYS(("mIID2NativeInterfaceMap @ %x with %d interface(s)",  \
+                        mIID2NativeInterfaceMap, mIID2NativeInterfaceMap ?    \
+                        mIID2NativeInterfaceMap->Count() : 0));
+
+        XPC_LOG_ALWAYS(("mClassInfo2NativeSetMap @ %x with %d sets(s)",       \
+                        mClassInfo2NativeSetMap, mClassInfo2NativeSetMap ?    \
+                        mClassInfo2NativeSetMap->Count() : 0));
+
+        XPC_LOG_ALWAYS(("mThisTranslatorMap @ %x with %d translator(s)",      \
+                        mThisTranslatorMap, mThisTranslatorMap ?              \
+                        mThisTranslatorMap->Count() : 0));
+
+        XPC_LOG_ALWAYS(("mNativeSetMap @ %x with %d sets(s)",                 \
+                        mNativeSetMap, mNativeSetMap ?                        \
+                        mNativeSetMap->Count() : 0));
+
+        // iterate sets...
+        if (depth && mNativeSetMap && mNativeSetMap->Count()) {
+            XPC_LOG_INDENT();
+            mNativeSetMap->Enumerate(NativeSetDumpEnumerator, &depth);
+            XPC_LOG_OUTDENT();
+        }
+
+        XPC_LOG_OUTDENT();
+#endif
+}
+
+/***************************************************************************/
+
+void
+XPCRootSetElem::AddToRootSet(XPCRootSetElem **listHead)
+{
+    MOZ_ASSERT(!mSelfp, "Must be not linked");
+
+    mSelfp = listHead;
+    mNext = *listHead;
+    if (mNext) {
+        MOZ_ASSERT(mNext->mSelfp == listHead, "Must be list start");
+        mNext->mSelfp = &mNext;
+    }
+    *listHead = this;
+}
+
+void
+XPCRootSetElem::RemoveFromRootSet()
+{
+    nsXPConnect *xpc = nsXPConnect::XPConnect();
+    JS::PokeGC(xpc->GetRuntime()->Runtime());
+
+    MOZ_ASSERT(mSelfp, "Must be linked");
+
+    MOZ_ASSERT(*mSelfp == this, "Link invariant");
+    *mSelfp = mNext;
+    if (mNext)
+        mNext->mSelfp = mSelfp;
+#ifdef DEBUG
+    mSelfp = nullptr;
+    mNext = nullptr;
+#endif
+}
+
+void
+XPCJSRuntime::AddGCCallback(xpcGCCallback cb)
+{
+    MOZ_ASSERT(cb, "null callback");
+    extraGCCallbacks.AppendElement(cb);
+}
+
+void
+XPCJSRuntime::RemoveGCCallback(xpcGCCallback cb)
+{
+    MOZ_ASSERT(cb, "null callback");
+    bool found = extraGCCallbacks.RemoveElement(cb);
+    if (!found) {
+        NS_ERROR("Removing a callback which was never added.");
+    }
+}
+
+void
+XPCJSRuntime::AddContextCallback(xpcContextCallback cb)
+{
+    MOZ_ASSERT(cb, "null callback");
+    extraContextCallbacks.AppendElement(cb);
+}
+
+void
+XPCJSRuntime::RemoveContextCallback(xpcContextCallback cb)
+{
+    MOZ_ASSERT(cb, "null callback");
+    bool found = extraContextCallbacks.RemoveElement(cb);
+    if (!found) {
+        NS_ERROR("Removing a callback which was never added.");
+    }
+}
+
+JSObject *
+XPCJSRuntime::GetJunkScope()
+{
+    if (!mJunkScope) {
+        AutoSafeJSContext cx;
+        SandboxOptions options;
+        options.sandboxName.AssignLiteral("XPConnect Junk Compartment");
+        RootedValue v(cx);
+        nsresult rv = CreateSandboxObject(cx, &v, nsContentUtils::GetSystemPrincipal(), options);
+        NS_ENSURE_SUCCESS(rv, nullptr);
+
+        mJunkScope = js::UncheckedUnwrap(&v.toObject());
+    }
+    return mJunkScope;
+}
+
+JSObject *
+XPCJSRuntime::GetCompilationScope()
+{
+    if (!mCompilationScope) {
+        AutoSafeJSContext cx;
+        SandboxOptions options;
+        options.sandboxName.AssignLiteral("XPConnect Compilation Compartment");
+        options.invisibleToDebugger = true;
+        options.discardSource = ShouldDiscardSystemSource();
+        RootedValue v(cx);
+        nsresult rv = CreateSandboxObject(cx, &v, /* principal = */ nullptr, options);
+        NS_ENSURE_SUCCESS(rv, nullptr);
+
+        mCompilationScope = js::UncheckedUnwrap(&v.toObject());
+    }
+    return mCompilationScope;
+}
+
+
+void
+XPCJSRuntime::DeleteSingletonScopes()
+{
+    mJunkScope = nullptr;
+    mCompilationScope = nullptr;
+}