diff -r 000000000000 -r 6474c204b198 js/xpconnect/loader/mozJSLoaderUtils.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/loader/mozJSLoaderUtils.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,94 @@
+/* -*- 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/. */
+
+#include "nsAutoPtr.h"
+
+#include "jsapi.h"
+#include "js/OldDebugAPI.h"
+
+#include "nsJSPrincipals.h"
+
+#include "mozilla/scache/StartupCache.h"
+
+using namespace JS;
+using namespace mozilla::scache;
+
+// We only serialize scripts with system principals. So we don't serialize the
+// principals when writing a script. Instead, when reading it back, we set the
+// principals to the system principals.
+nsresult
+ReadCachedScript(StartupCache* cache, nsACString &uri, JSContext *cx,
+                 nsIPrincipal *systemPrincipal, MutableHandleScript scriptp)
+{
+    nsAutoArrayPtr<char> buf;
+    uint32_t len;
+    nsresult rv = cache->GetBuffer(PromiseFlatCString(uri).get(),
+                                   getter_Transfers(buf), &len);
+    if (NS_FAILED(rv))
+        return rv; // don't warn since NOT_AVAILABLE is an ok error
+
+    scriptp.set(JS_DecodeScript(cx, buf, len, nullptr));
+    if (!scriptp)
+        return NS_ERROR_OUT_OF_MEMORY;
+    return NS_OK;
+}
+
+nsresult
+ReadCachedFunction(StartupCache* cache, nsACString &uri, JSContext *cx,
+                   nsIPrincipal *systemPrincipal, JSFunction **functionp)
+{
+    return NS_ERROR_FAILURE;
+/*  This doesn't actually work ...
+    nsAutoArrayPtr<char> buf;
+    uint32_t len;
+    nsresult rv = cache->GetBuffer(PromiseFlatCString(uri).get(),
+                                   getter_Transfers(buf), &len);
+    if (NS_FAILED(rv))
+        return rv; // don't warn since NOT_AVAILABLE is an ok error
+
+    JSObject *obj = JS_DecodeInterpretedFunction(cx, buf, len, nsJSPrincipals::get(systemPrincipal), nullptr);
+    if (!obj)
+        return NS_ERROR_OUT_OF_MEMORY;
+    JSFunction* function = JS_ValueToFunction(cx, OBJECT_TO_JSVAL(obj));
+    *functionp = function;
+    return NS_OK;*/
+}
+
+nsresult
+WriteCachedScript(StartupCache* cache, nsACString &uri, JSContext *cx,
+                  nsIPrincipal *systemPrincipal, HandleScript script)
+{
+    MOZ_ASSERT(JS_GetScriptPrincipals(script) == nsJSPrincipals::get(systemPrincipal));
+    MOZ_ASSERT(JS_GetScriptOriginPrincipals(script) == nsJSPrincipals::get(systemPrincipal));
+
+    uint32_t size;
+    void *data = JS_EncodeScript(cx, script, &size);
+    if (!data)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    MOZ_ASSERT(size);
+    nsresult rv = cache->PutBuffer(PromiseFlatCString(uri).get(), static_cast<char *>(data), size);
+    js_free(data);
+    return rv;
+}
+
+nsresult
+WriteCachedFunction(StartupCache* cache, nsACString &uri, JSContext *cx,
+                    nsIPrincipal *systemPrincipal, JSFunction *function)
+{
+    return NS_ERROR_FAILURE;
+/* This doesn't actually work ...
+    uint32_t size;
+    void *data =
+      JS_EncodeInterpretedFunction(cx, JS_GetFunctionObject(function), &size);
+    if (!data)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    MOZ_ASSERT(size);
+    nsresult rv = cache->PutBuffer(PromiseFlatCString(uri).get(), static_cast<char *>(data), size);
+    js_free(data);
+    return rv;*/
+}