diff -r 000000000000 -r 6474c204b198 layout/generic/nsIStatefulFrame.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/generic/nsIStatefulFrame.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+/* 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/. */
+
+/*
+ * interface for rendering objects whose state is saved in
+ * session-history (back-forward navigation)
+ */
+
+#ifndef _nsIStatefulFrame_h
+#define _nsIStatefulFrame_h
+
+#include "nsQueryFrame.h"
+
+class nsPresState;
+
+class nsIStatefulFrame
+{
+ public: 
+  NS_DECL_QUERYFRAME_TARGET(nsIStatefulFrame)
+
+  // Save the state for this frame.  If this method succeeds, the caller is
+  // responsible for deleting the resulting state when done with it.
+  NS_IMETHOD SaveState(nsPresState** aState) = 0;
+
+  // Restore the state for this frame from aState
+  NS_IMETHOD RestoreState(nsPresState* aState) = 0;
+};
+
+#endif /* _nsIStatefulFrame_h */