diff -r 000000000000 -r 6474c204b198 xpcom/glue/nsIWeakReferenceUtils.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/glue/nsIWeakReferenceUtils.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,108 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* 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 nsIWeakReferenceUtils_h__
+#define nsIWeakReferenceUtils_h__
+
+#include "nsCOMPtr.h"
+#include "nsIWeakReference.h"
+
+typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
+
+/**
+ *
+ */
+
+// a type-safe shortcut for calling the |QueryReferent()| member function
+// T must inherit from nsIWeakReference, but the cast may be ambiguous.
+template <class T, class DestinationType>
+inline
+nsresult
+CallQueryReferent( T* aSource, DestinationType** aDestination )
+  {
+    NS_PRECONDITION(aSource, "null parameter");
+    NS_PRECONDITION(aDestination, "null parameter");
+
+    return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
+                                  reinterpret_cast<void**>(aDestination));
+  }
+
+
+class NS_COM_GLUE nsQueryReferent : public nsCOMPtr_helper
+  {
+    public:
+      nsQueryReferent( nsIWeakReference* aWeakPtr, nsresult* error )
+          : mWeakPtr(aWeakPtr),
+            mErrorPtr(error)
+        {
+          // nothing else to do here
+        }
+
+      virtual nsresult NS_FASTCALL operator()( const nsIID& aIID, void** ) const;
+
+    private:
+      nsIWeakReference*  mWeakPtr;
+      nsresult*          mErrorPtr;
+  };
+
+inline
+const nsQueryReferent
+do_QueryReferent( nsIWeakReference* aRawPtr, nsresult* error = 0 )
+  {
+    return nsQueryReferent(aRawPtr, error);
+  }
+
+
+  /**
+   * Deprecated, use |do_GetWeakReference| instead.
+   */
+extern NS_COM_GLUE
+nsIWeakReference*
+NS_GetWeakReference( nsISupports* , nsresult* aResult=0 );
+
+  /**
+   * |do_GetWeakReference| is a convenience function that bundles up all the work needed
+   * to get a weak reference to an arbitrary object, i.e., the |QueryInterface|, test, and
+   * call through to |GetWeakReference|, and put it into your |nsCOMPtr|.
+   * It is specifically designed to cooperate with |nsCOMPtr| (or |nsWeakPtr|) like so:
+   * |nsWeakPtr myWeakPtr = do_GetWeakReference(aPtr);|.
+   */
+inline
+already_AddRefed<nsIWeakReference>
+do_GetWeakReference( nsISupports* aRawPtr, nsresult* error = 0 )
+  {
+    return dont_AddRef(NS_GetWeakReference(aRawPtr, error));
+  }
+
+inline
+void
+do_GetWeakReference( nsIWeakReference* aRawPtr, nsresult* error = 0 )
+  {
+    // This signature exists solely to _stop_ you from doing a bad thing.
+    //  Saying |do_GetWeakReference()| on a weak reference itself,
+    //  is very likely to be a programmer error.
+  }
+
+template <class T>
+inline
+void
+do_GetWeakReference( already_AddRefed<T>& )
+  {
+    // This signature exists solely to _stop_ you from doing the bad thing.
+    //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
+    //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
+  }
+
+template <class T>
+inline
+void
+do_GetWeakReference( already_AddRefed<T>&, nsresult* )
+  {
+    // This signature exists solely to _stop_ you from doing the bad thing.
+    //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
+    //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
+  }
+
+#endif