Have Element::ensureMutableInlineStyle() return a reference

Source/core/css/CSSKeyframeRule.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 37 matching lines @@
 
     // Exposed to JavaScript.
     String keyText() const;
     void setKeyText(const String&);
 
     // Used by StyleResolver.
     const Vector<double>& keys() const;
     // Used by BisonCSSParser when constructing a new StyleKeyframe.
     void setKeys(PassOwnPtr<Vector<double> >);
 
-    const StylePropertySet* properties() const { return m_properties.get(); }
-    MutableStylePropertySet* mutableProperties();
+    const StylePropertySet& properties() const { return *m_properties; }
+    MutableStylePropertySet& mutableProperties();
     void setProperties(PassRefPtr<StylePropertySet>);
 
     String cssText() const;
 
     static PassOwnPtr<Vector<double> > createKeyList(CSSParserValueList*);
 
 private:
     StyleKeyframe();
 
     RefPtr<StylePropertySet> m_properties;
@@ skipping 24 matching lines @@
     mutable RefPtr<StyleRuleCSSStyleDeclaration> m_propertiesCSSOMWrapper;
 
     friend class CSSKeyframesRule;
 };
 
 DEFINE_CSS_RULE_TYPE_CASTS(CSSKeyframeRule, KEYFRAME_RULE);
 
 } // namespace WebCore
 
 #endif // CSSKeyframeRule_h