Remove code that is unused after ContextMenu cleanup

Source/core/history/BackForwardController.h

 /*
  * Copyright (C) 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 28 matching lines @@
 // FIXME: Why does this class exist? It seems to delegate almost entirely to Page, and perhaps should be part of Page's implementation.
 class BackForwardController {
     WTF_MAKE_NONCOPYABLE(BackForwardController); WTF_MAKE_FAST_ALLOCATED;
 public:
     ~BackForwardController();
 
     static PassOwnPtr<BackForwardController> create(Page*, BackForwardClient*);
 
     BackForwardClient* client() const { return m_client; }
 
-    bool canGoBackOrForward(int distance) const;
     void goBackOrForward(int distance);
 
     bool goBack();
     bool goForward();
 
     void addItem(PassRefPtr<HistoryItem>);
     void setCurrentItem(HistoryItem*);
         
     int count() const;
     int backCount() const;
@@ skipping 12 matching lines @@
 private:
     BackForwardController(Page*, BackForwardClient*);
 
     Page* m_page;
     BackForwardClient* m_client;
 };
 
 } // namespace WebCore
 
 #endif // BackForwardController_h