diff -r 000000000000 -r 6474c204b198 js/public/WeakMapPtr.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/public/WeakMapPtr.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/* -*- 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/. */
+
+#ifndef js_WeakMapPtr_h
+#define js_WeakMapPtr_h
+
+#include "jspubtd.h"
+
+#include "js/TypeDecls.h"
+
+namespace JS {
+
+// A wrapper around the internal C++ representation of SpiderMonkey WeakMaps,
+// usable outside the engine.
+//
+// The supported template specializations are enumerated in WeakMapPtr.cpp. If
+// you want to use this class for a different key/value combination, add it to
+// the list and the compiler will generate the relevant machinery.
+template <typename K, typename V>
+class JS_PUBLIC_API(WeakMapPtr)
+{
+  public:
+    WeakMapPtr() : ptr(nullptr) {};
+    bool init(JSContext *cx);
+    bool initialized() { return ptr != nullptr; };
+    void destroy();
+    virtual ~WeakMapPtr() { MOZ_ASSERT(!initialized()); }
+    void trace(JSTracer *tracer);
+
+    V lookup(const K &key);
+    bool put(JSContext *cx, const K &key, const V &value);
+
+    static void keyMarkCallback(JSTracer *trc, K key, void *data);
+
+  private:
+    void *ptr;
+
+    // WeakMapPtr is neither copyable nor assignable.
+    WeakMapPtr(const WeakMapPtr &wmp) MOZ_DELETE;
+    WeakMapPtr &operator=(const WeakMapPtr &wmp) MOZ_DELETE;
+};
+
+} /* namespace JS */
+
+#endif  /* js_WeakMapPtr_h */