Clean up forward declarations in Source/core/page

Source/core/page/EditorClient.h

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
@@ skipping 14 matching lines @@
  */
 
 #ifndef EditorClient_h
 #define EditorClient_h
 
 #include "core/editing/SelectionType.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 
-class Element;
 class LocalFrame;
-class UndoStep;
 
 class EditorClient {
 public:
     virtual ~EditorClient() { }
 
     virtual void respondToChangedContents() = 0;
     virtual void respondToChangedSelection(LocalFrame*, SelectionType) = 0;
 
     virtual bool canCopyCut(LocalFrame*, bool defaultValue) const = 0;
     virtual bool canPaste(LocalFrame*, bool defaultValue) const = 0;
 
     virtual bool handleKeyboardEvent() = 0;
 };
 
 }
 
 #endif // EditorClient_h