diff -r 000000000000 -r 6474c204b198 modules/libpref/public/nsIPrefBranch2.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/libpref/public/nsIPrefBranch2.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,16 @@
+/* -*- Mode: IDL; 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/. */
+
+#include "nsIPrefBranch.idl"
+
+/**
+ * An empty interface to provide backwards compatibility for existing code.
+ *
+ * @see nsIPrefBranch
+ */
+[scriptable, uuid(8892016d-07f7-4530-b5c1-d73dfcde4a1c)]
+interface nsIPrefBranch2 : nsIPrefBranch
+{
+};