diff -r 000000000000 -r 6474c204b198 js/xpconnect/src/XPCWrapper.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/src/XPCWrapper.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#include "xpcprivate.h"
+#include "XPCWrapper.h"
+#include "WrapperFactory.h"
+#include "AccessCheck.h"
+
+using namespace xpc;
+using namespace mozilla;
+
+namespace XPCNativeWrapper {
+
+static inline
+bool
+ThrowException(nsresult ex, JSContext *cx)
+{
+  XPCThrower::Throw(ex, cx);
+
+  return false;
+}
+
+static bool
+UnwrapNW(JSContext *cx, unsigned argc, jsval *vp)
+{
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  if (args.length() != 1) {
+    return ThrowException(NS_ERROR_XPC_NOT_ENOUGH_ARGS, cx);
+  }
+
+  JS::RootedValue v(cx, args[0]);
+  if (!v.isObject() || !js::IsWrapper(&v.toObject())) {
+    args.rval().set(v);
+    return true;
+  }
+
+  if (AccessCheck::wrapperSubsumes(&v.toObject())) {
+    bool ok = xpc::WrapperFactory::WaiveXrayAndWrap(cx, &v);
+    NS_ENSURE_TRUE(ok, false);
+  }
+
+  args.rval().set(v);
+  return true;
+}
+
+static bool
+XrayWrapperConstructor(JSContext *cx, unsigned argc, jsval *vp)
+{
+  JS::CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() == 0) {
+    return ThrowException(NS_ERROR_XPC_NOT_ENOUGH_ARGS, cx);
+  }
+
+  if (!args[0].isObject()) {
+    args.rval().set(args[0]);
+    return true;
+  }
+
+  args.rval().setObject(*js::UncheckedUnwrap(&args[0].toObject()));
+  return JS_WrapValue(cx, args.rval());
+}
+// static
+bool
+AttachNewConstructorObject(JSContext *aCx, JS::HandleObject aGlobalObject)
+{
+  // Pushing a JSContext calls ActivateDebugger which calls this function, so
+  // we can't use an AutoJSContext here until JSD is gone.
+  JSAutoCompartment ac(aCx, aGlobalObject);
+  JSFunction *xpcnativewrapper =
+    JS_DefineFunction(aCx, aGlobalObject, "XPCNativeWrapper",
+                      XrayWrapperConstructor, 1,
+                      JSPROP_READONLY | JSPROP_PERMANENT | JSFUN_STUB_GSOPS | JSFUN_CONSTRUCTOR);
+  if (!xpcnativewrapper) {
+    return false;
+  }
+  JS::RootedObject obj(aCx, JS_GetFunctionObject(xpcnativewrapper));
+  return JS_DefineFunction(aCx, obj, "unwrap", UnwrapNW, 1,
+                           JSPROP_READONLY | JSPROP_PERMANENT) != nullptr;
+}
+
+} // namespace XPCNativeWrapper
+
+namespace XPCWrapper {
+
+JSObject *
+UnsafeUnwrapSecurityWrapper(JSObject *obj)
+{
+  if (js::IsProxy(obj)) {
+    return js::UncheckedUnwrap(obj);
+  }
+
+  return obj;
+}
+
+} // namespace XPCWrapper