diff -r 000000000000 -r 6474c204b198 docshell/base/nsIPrivacyTransitionObserver.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/docshell/base/nsIPrivacyTransitionObserver.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,11 @@
+/* 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 "nsISupports.idl"
+
+[scriptable, function, uuid(b4b1449d-0ef0-47f5-b62e-adc57fd49702)]
+interface nsIPrivacyTransitionObserver : nsISupports
+{
+  void privateModeChanged(in bool enabled);
+};