diff -r 000000000000 -r 6474c204b198 content/base/src/nsCCUncollectableMarker.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/base/src/nsCCUncollectableMarker.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef nsCCUncollectableMarker_h_
+#define nsCCUncollectableMarker_h_
+
+#include "js/TracingAPI.h"
+#include "mozilla/Attributes.h"
+#include "nsIObserver.h"
+
+class nsCCUncollectableMarker MOZ_FINAL : public nsIObserver
+{
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  /**
+   * Inits a global nsCCUncollectableMarker. Should only be called once.
+   */
+  static nsresult Init();
+
+  /**
+   * Checks if we're collecting during a given generation
+   */
+  static bool InGeneration(uint32_t aGeneration)
+  {
+    return aGeneration && aGeneration == sGeneration;
+  }
+
+  template <class CCCallback>
+  static bool InGeneration(CCCallback& aCb, uint32_t aGeneration)
+  {
+    return InGeneration(aGeneration) && !aCb.WantAllTraces();
+  }
+
+  static uint32_t sGeneration;
+
+private:
+  nsCCUncollectableMarker() {}
+
+};
+
+namespace mozilla {
+namespace dom {
+void TraceBlackJS(JSTracer* aTrc, uint32_t aGCNumber, bool aIsShutdownGC);
+}
+}
+
+#endif