Clean up forward declarations in Source/core

Source/core/dom/StyleElement.h

 /*
  * Copyright (C) 2006, 2007 Rob Buis
  *
  * 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
@@ skipping 11 matching lines @@
 #define StyleElement_h
 
 #include "core/css/CSSStyleSheet.h"
 #include "wtf/text/TextPosition.h"
 
 namespace blink {
 
 class ContainerNode;
 class Document;
 class Element;
-class TreeScope;
 
 class StyleElement : public WillBeGarbageCollectedMixin {
 public:
     StyleElement(Document*, bool createdByParser);
     virtual ~StyleElement();
     virtual void trace(Visitor*);
 
 protected:
     virtual const AtomicString& type() const = 0;
     virtual const AtomicString& media() const = 0;
@@ skipping 20 matching lines @@
 
     bool m_createdByParser : 1;
     bool m_loading : 1;
     bool m_registeredAsCandidate : 1;
     TextPosition m_startPosition;
 };
 
 }
 
 #endif