StyleResolver should update RuleSets lazily.

Source/core/css/resolver/ScopedStyleResolver.cpp

Index: Source/core/css/resolver/ScopedStyleResolver.cpp
diff --git a/Source/core/css/resolver/ScopedStyleResolver.cpp b/Source/core/css/resolver/ScopedStyleResolver.cpp
index b748dde0c21d8469c48ce453a1574de4f069afbf..a3dd4ee6d8f0a37674ff752d1d2642aa0c5902e0 100644
--- a/Source/core/css/resolver/ScopedStyleResolver.cpp
+++ b/Source/core/css/resolver/ScopedStyleResolver.cpp
@@ -65,17 +65,30 @@ ContainerNode* ScopedStyleResolver::scopingNodeFor(const CSSStyleSheet* sheet)
     return (parent->isElementNode() || parent->isShadowRoot()) ? parent : 0;
 }
 
-void ScopedStyleResolver::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvaluator& medium, StyleResolver* resolver)
+inline RuleSet* ScopedStyleResolver::ensureAuthorStyle()
 {
     if (!m_authorStyle)
         m_authorStyle = RuleSet::create();
+    return m_authorStyle.get();
+}
+
+void ScopedStyleResolver::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvaluator& medium, StyleResolver* resolver, bool viewportRuleIsProcessed)
+{
+    AddRuleFlags addRuleFlags = resolver->document().securityOrigin()->canRequest(sheet->baseURL()) ? RuleHasDocumentSecurityOrigin : RuleHasNoSpecialState;
+
+    if (viewportRuleIsProcessed)
+        addRuleFlags = static_cast<AddRuleFlags>(addRuleFlags | ViewportRuleIsProcessed);
 
-    bool hasDocumentSecurityOrigin = resolver->document().securityOrigin()->canRequest(sheet->baseURL());
-    m_authorStyle->addRulesFromSheet(sheet, medium, hasDocumentSecurityOrigin);
+    ensureAuthorStyle()->addRulesFromSheet(sheet, medium, addRuleFlags);
     resolver->addMediaQueryResults(m_authorStyle->viewportDependentMediaQueryResults());
     resolver->processScopedRules(*m_authorStyle, sheet->baseURL(), &m_scopingNode);
 }
 
+void ScopedStyleResolver::addViewportRule(StyleRuleViewport* rule)
+{
+    ensureAuthorStyle()->addViewportRule(rule);
+}
+
 inline RuleSet* ScopedStyleResolver::ensureAtHostRuleSetFor(const ShadowRoot* shadowRoot)
 {
     HashMap<const ShadowRoot*, OwnPtr<RuleSet> >::AddResult addResult = m_atHostRules.add(shadowRoot, nullptr);