blink: Cleanup core class forward declarations

third_party/WebKit/Source/core/page/PageVisibilityNotifier.h

 /*
  * Copyright (C) 2013 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:
  * 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 13 matching lines @@
  */
 
 #ifndef PageVisibilityNotifier_h
 #define PageVisibilityNotifier_h
 
 #include "core/CoreExport.h"
 #include "platform/LifecycleNotifier.h"
 
 namespace blink {
 
-class LocalFrame;
 class Page;
 class PageVisibilityObserver;
 
 class CORE_EXPORT PageVisibilityNotifier
     : public LifecycleNotifier<Page, PageVisibilityObserver> {
  public:
   void notifyPageVisibilityChanged();
 };
 
 }  // namespace blink
 
 #endif  // PageVisibilityNotifier_h