Ensure that FrameLoadTypeBackForward only occurs once per navigation.

Source/core/loader/FrameLoader.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
@@ skipping 63 matching lines @@
     ~FrameLoader();
 
     void init();
 
     MixedContentChecker* mixedContentChecker() const { return &m_mixedContentChecker; }
     ProgressTracker& progress() const { return *m_progressTracker; }
 
     // These functions start a load. All eventually call into loadWithNavigationAction() or loadInSameDocument().
     void load(const FrameLoadRequest&); // The entry point for non-reload, non-history loads.
     void reload(ReloadPolicy, const KURL& overrideURL = KURL(), ClientRedirectPolicy = NotClientRedirect);
-    void loadHistoryItem(HistoryItem*, HistoryLoadType = HistoryDifferentDocumentLoad, ResourceRequestCachePolicy = UseProtocolCachePolicy); // The entry point for all back/forward loads
+    void loadHistoryItem(HistoryItem*, FrameLoadType = FrameLoadTypeBackForward,
+        HistoryLoadType = HistoryDifferentDocumentLoad,
+        ResourceRequestCachePolicy = UseProtocolCachePolicy); // The entry point for all back/forward loads
 
     static void reportLocalLoadFailed(LocalFrame*, const String& url);
 
     // FIXME: These are all functions which stop loads. We have too many.
     // Warning: stopAllLoaders can and will detach the LocalFrame out from under you. All callers need to either protect the LocalFrame
     // or guarantee they won't in any way access the LocalFrame after stopAllLoaders returns.
     void stopAllLoaders();
     void stopLoading();
     bool closeURL();
 
@@ skipping 169 matching lines @@
 
     bool m_didAccessInitialDocument;
     Timer<FrameLoader> m_didAccessInitialDocumentTimer;
 
     SandboxFlags m_forcedSandboxFlags;
 };
 
 } // namespace blink
 
 #endif // FrameLoader_h