Move CSSOM classes to using MutableStylePropertySet over StylePropertySet.

Source/core/css/WebKitCSSKeyframeRule.h

 /*
  * Copyright (C) 2007, 2008, 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 13 matching lines @@
  */
 
 #ifndef WebKitCSSKeyframeRule_h
 #define WebKitCSSKeyframeRule_h
 
 #include "core/css/CSSRule.h"
 
 namespace WebCore {
 
 class CSSStyleDeclaration;
+class MutableStylePropertySet;
 class StylePropertySet;
 class StyleRuleCSSStyleDeclaration;
 class WebKitCSSKeyframesRule;
 
 class StyleKeyframe : public RefCounted<StyleKeyframe> {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<StyleKeyframe> create()
     {
         return adoptRef(new StyleKeyframe());
     }
     ~StyleKeyframe();
 
     String keyText() const { return m_key; }
     void setKeyText(const String& s) { m_key = s; }
 
     void getKeys(Vector<float>& keys) const   { parseKeyString(m_key, keys); }
     
     const StylePropertySet* properties() const { return m_properties.get(); }
-    StylePropertySet* mutableProperties();
+    MutableStylePropertySet* mutableProperties();
     void setProperties(PassRefPtr<StylePropertySet>);
     
     String cssText() const;
 
     void reportMemoryUsage(MemoryObjectInfo*) const;
 
 private:
     StyleKeyframe();
     
     static void parseKeyString(const String&, Vector<float>& keys);
@@ skipping 23 matching lines @@
 
     RefPtr<StyleKeyframe> m_keyframe;
     mutable RefPtr<StyleRuleCSSStyleDeclaration> m_propertiesCSSOMWrapper;
     
     friend class WebKitCSSKeyframesRule;
 };
 
 } // namespace WebCore
 
 #endif // WebKitCSSKeyframeRule_h