Reduce forward declarations in core/dom

Source/core/dom/shadow/SelectRuleFeatureSet.h

 /*
  * Copyright (C) 2012 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
  */
 
 #ifndef SelectRuleFeatureSet_h
 #define SelectRuleFeatureSet_h
 
 #include "core/css/RuleFeature.h"
 #include "core/dom/Element.h"
 
 namespace WebCore {
 
-class Element;
 class SpaceSplitString;
 
 class SelectRuleFeatureSet {
     DISALLOW_ALLOCATION();
 public:
     SelectRuleFeatureSet();
 
     void add(const SelectRuleFeatureSet&);
     void clear();
     void collectFeaturesFromSelector(const CSSSelector&);
@@ skipping 38 matching lines @@
 
 inline bool SelectRuleFeatureSet::hasSelectorForAttribute(const AtomicString& attributeName) const
 {
     ASSERT(!attributeName.isEmpty());
     return m_cssRuleFeatureSet.hasSelectorForAttribute(attributeName);
 }
 
 }
 
 #endif