Clean up forward declarations in Source/core

Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h

 /*
  * Copyright (C) 2010 Julien Chaffraix <jchaffraix@webkit.org>
  * All right 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
@@ skipping 20 matching lines @@
 #include "platform/heap/Handle.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/Vector.h"
 #include "wtf/text/AtomicString.h"
 
 namespace blink {
 
 class Event;
 class EventTarget;
-class XMLHttpRequestProgressEvent;
 
 // This class implements the XHR2 ProgressEvent dispatching:
 //   "dispatch a progress event named progress about every 50ms or for every
 //   byte received, whichever is least frequent".
 //
 // readystatechange events also go through this class since ProgressEvents and
 // readystatechange events affect each other.
 //
 // In the comments for this class:
 // - "progress" event means an event named "progress"
@@ skipping 46 matching lines @@
     RawPtrWillBeMember<EventTarget> m_target;
 
     // A slot for the deferred "progress" ProgressEvent. When multiple events
     // arrive, only the last one is stored and others are discarded.
     const OwnPtr<DeferredEvent> m_deferred;
 };
 
 } // namespace blink
 
 #endif // XMLHttpRequestProgressEventThrottle_h