diff -r 000000000000 -r 6474c204b198 layout/xul/nsIScrollbarMediator.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/xul/nsIScrollbarMediator.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; 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/. */
+
+#ifndef nsIScrollbarMediator_h___
+#define nsIScrollbarMediator_h___
+
+#include "nsQueryFrame.h"
+
+class nsScrollbarFrame;
+
+class nsIScrollbarMediator
+{
+public:
+  NS_DECL_QUERYFRAME_TARGET(nsIScrollbarMediator)
+
+  // The aScrollbar argument denotes the scrollbar that's firing the notification.
+  NS_IMETHOD PositionChanged(nsScrollbarFrame* aScrollbar, int32_t aOldIndex, int32_t& aNewIndex) = 0;
+  NS_IMETHOD ScrollbarButtonPressed(nsScrollbarFrame* aScrollbar, int32_t aOldIndex, int32_t aNewIndex) = 0;
+
+  NS_IMETHOD VisibilityChanged(bool aVisible) = 0;
+};
+
+#endif
+