Clean up forward declarations in Source/core/css

Source/core/css/StyleRule.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2006, 2008, 2012, 2013 Apple Inc. All rights reserved.
  *
  * 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.
  *
@@ skipping 12 matching lines @@
 #define StyleRule_h
 
 #include "core/css/CSSSelectorList.h"
 #include "core/css/MediaList.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class CSSRule;
-class CSSStyleRule;
 class CSSStyleSheet;
 class MutableStylePropertySet;
 class StylePropertySet;
 
 class StyleRuleBase : public RefCountedWillBeGarbageCollectedFinalized<StyleRuleBase> {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     enum Type {
         Unknown, // Not used.
         Style,
@@ skipping 243 matching lines @@
 DEFINE_STYLE_RULE_TYPE_CASTS(FontFace);
 DEFINE_STYLE_RULE_TYPE_CASTS(Page);
 DEFINE_STYLE_RULE_TYPE_CASTS(Media);
 DEFINE_STYLE_RULE_TYPE_CASTS(Supports);
 DEFINE_STYLE_RULE_TYPE_CASTS(Viewport);
 DEFINE_STYLE_RULE_TYPE_CASTS(Filter);
 
 } // namespace blink
 
 #endif // StyleRule_h