diff -r 000000000000 -r 6474c204b198 dom/bindings/CallbackFunction.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/bindings/CallbackFunction.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/. */
+
+/**
+ * A common base class for representing WebIDL callback function types in C++.
+ *
+ * This class implements common functionality like lifetime
+ * management, initialization with the callable, and setup of the call
+ * environment.  Subclasses corresponding to particular callback
+ * function types should provide a Call() method that actually does
+ * the call.
+ */
+
+#ifndef mozilla_dom_CallbackFunction_h
+#define mozilla_dom_CallbackFunction_h
+
+#include "mozilla/dom/CallbackObject.h"
+
+namespace mozilla {
+namespace dom {
+
+class CallbackFunction : public CallbackObject
+{
+public:
+  explicit CallbackFunction(JS::Handle<JSObject*> aCallable,
+                            nsIGlobalObject* aIncumbentGlobal)
+    : CallbackObject(aCallable, aIncumbentGlobal)
+  {
+  }
+
+  JS::Handle<JSObject*> Callable() const
+  {
+    return Callback();
+  }
+
+  bool HasGrayCallable() const
+  {
+    // Play it safe in case this gets called after unlink.
+    return mCallback && xpc_IsGrayGCThing(mCallback);
+  }
+
+protected:
+  explicit CallbackFunction(CallbackFunction* aCallbackFunction)
+    : CallbackObject(aCallbackFunction)
+  {
+  }
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_CallbackFunction_h