Revert of Move UndoStack from Page to Editor

third_party/WebKit/Source/core/editing/commands/UndoStack.h

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
 
 #include "platform/heap/Handle.h"
 #include "wtf/Deque.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 
 class LocalFrame;
 class UndoStep;
 
-// |UndoStack| is owned by and always 1:1 to |Editor|. Since |Editor| is 1:1 to
-// |LocalFrame|, |UndoStack| is also 1:1 to |LocalFrame|.
 class UndoStack final : public GarbageCollected<UndoStack> {
     WTF_MAKE_NONCOPYABLE(UndoStack);
 public:
     static UndoStack* create();
 
     void registerUndoStep(UndoStep*);
     void registerRedoStep(UndoStep*);
+    void didUnloadFrame(const LocalFrame&);
     bool canUndo() const;
     bool canRedo() const;
     void undo();
     void redo();
 
     DECLARE_TRACE();
 
 private:
     UndoStack();
 
     typedef HeapDeque<Member<UndoStep>> UndoStepStack;
 
+    void filterOutUndoSteps(UndoStepStack&, const LocalFrame&);
+
     bool m_inRedo;
     UndoStepStack m_undoStack;
     UndoStepStack m_redoStack;
 };
 
 } // namespace blink
 
 #endif