StyleResolver should update RuleSets lazily.

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 138 matching lines @@
 
     PassRefPtr<StyleRuleFontFace> copy() const { return adoptRef(new StyleRuleFontFace(*this)); }
 
 private:
     StyleRuleFontFace();
     StyleRuleFontFace(const StyleRuleFontFace&);
 
     RefPtr<StylePropertySet> m_properties;
 };
 
+inline const StyleRuleFontFace* toStyleRuleFontFace(const StyleRuleBase* rule)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isFontFaceRule());
+    return static_cast<const StyleRuleFontFace*>(rule);
+}
+
 class StyleRulePage : public StyleRuleBase {
 public:
     static PassRefPtr<StyleRulePage> create() { return adoptRef(new StyleRulePage); }
 
     ~StyleRulePage();
 
     const CSSSelector* selector() const { return m_selectorList.first(); }
     const StylePropertySet* properties() const { return m_properties.get(); }
     MutableStylePropertySet* mutableProperties();
 
@@ skipping 114 matching lines @@
 
     RefPtr<StylePropertySet> m_properties;
 };
 
 inline const StyleRuleMedia* toStyleRuleMedia(const StyleRuleGroup* rule)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isMediaRule());
     return static_cast<const StyleRuleMedia*>(rule);
 }
 
+inline const StyleRuleMedia* toStyleRuleMedia(const StyleRuleBase* rule)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isMediaRule());
+    return static_cast<const StyleRuleMedia*>(rule);
+}
+
 inline const StyleRuleSupports* toStyleRuleSupports(const StyleRuleGroup* rule)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isSupportsRule());
     return static_cast<const StyleRuleSupports*>(rule);
 }
 
 inline const StyleRuleRegion* toStyleRuleRegion(const StyleRuleGroup* rule)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isRegionRule());
     return static_cast<const StyleRuleRegion*>(rule);
 }
 
+inline StyleRuleViewport* toStyleRuleViewport(StyleRuleBase* rule)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isViewportRule());
+    return static_cast<StyleRuleViewport*>(rule);
+}
+
 class StyleRuleFilter : public StyleRuleBase {
 public:
     static PassRefPtr<StyleRuleFilter> create(const String& filterName) { return adoptRef(new StyleRuleFilter(filterName)); }
 
     ~StyleRuleFilter();
 
     const String& filterName() const { return m_filterName; }
 
     const StylePropertySet* properties() const { return m_properties.get(); }
     MutableStylePropertySet* mutableProperties();
 
     void setProperties(PassRefPtr<StylePropertySet>);
 
     PassRefPtr<StyleRuleFilter> copy() const { return adoptRef(new StyleRuleFilter(*this)); }
 
 private:
     StyleRuleFilter(const String&);
     StyleRuleFilter(const StyleRuleFilter&);
 
     String m_filterName;
     RefPtr<StylePropertySet> m_properties;
 };
 
 } // namespace WebCore
 
 #endif // StyleRule_h