Don't store a RuleFeatureSet on ScopedStyleResolver.

sky/engine/core/css/StyleSheetContents.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2012 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 42 matching lines @@
 
     const CSSParserContext& parserContext() const { return m_parserContext; }
 
     bool parseString(const String&);
 
     void parserAppendRule(PassRefPtr<StyleRuleBase>);
 
     const Vector<RefPtr<StyleRuleBase> >& childRules() const { return m_childRules; }
 
     void shrinkToFit();
-    RuleSet& ruleSet() { ASSERT(m_ruleSet); return *m_ruleSet.get(); }
     RuleSet& ensureRuleSet();
 
 private:
     explicit StyleSheetContents(Document* document, const CSSParserContext&);
 
     OwnPtr<RuleSet> m_ruleSet;
     Vector<RefPtr<StyleRuleBase> > m_childRules;
     CSSParserContext m_parserContext;
 
     RefPtr<Document> m_document;
 };
 
 } // namespace
 
 #endif  // SKY_ENGINE_CORE_CSS_STYLESHEETCONTENTS_H_