Remove unused function UndoStep::belongsTo()

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

 /*
  * 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:
  *
  *     * 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 18 matching lines @@
  */
 
 #ifndef UndoStep_h
 #define UndoStep_h
 
 #include "core/events/InputEvent.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
-class LocalFrame;
-
 class UndoStep : public GarbageCollectedFinalized<UndoStep> {
  public:
   virtual ~UndoStep() {}
   DEFINE_INLINE_VIRTUAL_TRACE() {}
 
-  virtual bool belongsTo(const LocalFrame&) const = 0;
   virtual void unapply() = 0;
   virtual void reapply() = 0;
   virtual InputEvent::InputType inputType() const = 0;
 };
 
 }  // namespace blink
 
 #endif