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 95d6b8050bb077f6be9360a429cf4fbbb7fe4eba..bb87f1f9517301f9dd250b60dd3182cd31ceb458 100644
--- a/Source/core/css/resolver/ScopedStyleResolver.cpp
+++ b/Source/core/css/resolver/ScopedStyleResolver.cpp
@@ -247,14 +247,24 @@ const ContainerNode* ScopedStyleResolver::scopingNodeFor(const CSSStyleSheet* sh
     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();
-    m_authorStyle->addRulesFromSheet(sheet, medium, resolver, &m_scopingNode);
+    return m_authorStyle.get();
+}
+
+void ScopedStyleResolver::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvaluator& medium, StyleResolver* resolver, bool viewportRuleIsProcessed)
+{
+    ensureAuthorStyle()->addRulesFromSheet(sheet, medium, resolver, &m_scopingNode, viewportRuleIsProcessed);
     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);