Clean up forward declarations in Source/core/css

Source/core/css/MediaQueryListListener.h

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Library General Public License for more details.
  *
  *  You should have received a copy of the GNU Library General Public License
  *  along with this library; see the file COPYING.LIB.  If not, write to
  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  *  Boston, MA 02110-1301, USA.
  */
 
 #ifndef MediaQueryListListener_h
 #define MediaQueryListListener_h
 
 #include "core/css/MediaQueryList.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefCounted.h"
 
 namespace blink {
 
-class MediaQueryList;
-
 // See http://dev.w3.org/csswg/cssom-view/#the-mediaquerylist-interface
 class MediaQueryListListener : public RefCountedWillBeGarbageCollectedFinalized<MediaQueryListListener> {
 public:
     virtual ~MediaQueryListListener();
 
     virtual void notifyMediaQueryChanged() = 0;
 
     virtual void trace(Visitor* visitor) { }
 protected:
     MediaQueryListListener();
 };
 
 }
 
 #endif // MediaQueryListListener_h