Clean up forward declarations in Source/core/css

Source/core/css/PropertySetCSSStyleDeclaration.h

 /*
  * Copyright (C) 2012 Apple 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 14 matching lines @@
 
 #ifndef PropertySetCSSStyleDeclaration_h
 #define PropertySetCSSStyleDeclaration_h
 
 #include "core/css/CSSStyleDeclaration.h"
 #include "wtf/HashMap.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
-class CSSProperty;
 class CSSRule;
 class CSSValue;
 class Element;
 class ExceptionState;
 class MutableStylePropertySet;
 class StyleSheetContents;
 
 class AbstractPropertySetCSSStyleDeclaration : public CSSStyleDeclaration {
 public:
     virtual Element* parentElement() const { return 0; }
@@ skipping 105 matching lines @@
     virtual Element* parentElement() const OVERRIDE { return m_parentElement; }
 
     virtual void didMutate(MutationType) OVERRIDE;
 
     RawPtrWillBeMember<Element> m_parentElement;
 };
 
 } // namespace blink
 
 #endif