StyleResolver should update RuleSets lazily.

Source/core/css/RuleSet.cpp

Index: Source/core/css/RuleSet.cpp
diff --git a/Source/core/css/RuleSet.cpp b/Source/core/css/RuleSet.cpp
index f2fa53701061a08a790eb8899ead1a2adf013de3..97b459d9b2276a54a26337a8722fef21d17a61e7 100644
--- a/Source/core/css/RuleSet.cpp
+++ b/Source/core/css/RuleSet.cpp
@@ -51,11 +51,6 @@ using namespace HTMLNames;
 
 // -----------------------------------------------------------------
 
-static inline bool isDocumentScope(const ContainerNode* scope)
-{
-    return !scope || scope->isDocumentNode();
-}
-
 static inline bool isSelectorMatchingHTMLBasedOnRuleHash(const CSSSelector* selector)
 {
     ASSERT(selector);
@@ -404,7 +399,7 @@ void RuleSet::addChildRules(const Vector<RefPtr<StyleRuleBase> >& rules, const M
             addRegionRule(static_cast<StyleRuleRegion*>(rule), hasDocumentSecurityOrigin);
         } else if (rule->isHostRule()) {
             addHostRule(static_cast<StyleRuleHost*>(rule));
-        } else if (rule->isViewportRule()) {
+        } else if (rule->isViewportRule() && !(addRuleFlags & ViewportRuleIsProcessed)) {
             addViewportRule(static_cast<StyleRuleViewport*>(rule));
         } else if (rule->isSupportsRule() && static_cast<StyleRuleSupports*>(rule)->conditionIsSupported()) {
             addChildRules(static_cast<StyleRuleSupports*>(rule)->childRules(), medium, resolver, scope, hasDocumentSecurityOrigin, addRuleFlags);
@@ -412,7 +407,7 @@ void RuleSet::addChildRules(const Vector<RefPtr<StyleRuleBase> >& rules, const M
     }
 }
 
-void RuleSet::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvaluator& medium, StyleResolver* resolver, const ContainerNode* scope)
+void RuleSet::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvaluator& medium, StyleResolver* resolver, const ContainerNode* scope, bool viewportRuleIsProcessed)
 {
     ASSERT(sheet);
 
@@ -420,11 +415,11 @@ void RuleSet::addRulesFromSheet(StyleSheetContents* sheet, const MediaQueryEvalu
     for (unsigned i = 0; i < importRules.size(); ++i) {
         StyleRuleImport* importRule = importRules[i].get();
         if (importRule->styleSheet() && (!importRule->mediaQueries() || medium.eval(importRule->mediaQueries(), resolver->viewportDependentMediaQueryResults())))
-            addRulesFromSheet(importRule->styleSheet(), medium, resolver, scope);
+            addRulesFromSheet(importRule->styleSheet(), medium, resolver, scope, viewportRuleIsProcessed);
     }
 
     bool hasDocumentSecurityOrigin = resolver && resolver->document().securityOrigin()->canRequest(sheet->baseURL());
-    AddRuleFlags addRuleFlags = static_cast<AddRuleFlags>((hasDocumentSecurityOrigin ? RuleHasDocumentSecurityOrigin : 0) | (!scope ? RuleCanUseFastCheckSelector : 0));
+    AddRuleFlags addRuleFlags = static_cast<AddRuleFlags>((hasDocumentSecurityOrigin ? RuleHasDocumentSecurityOrigin : 0) | (!scope ? RuleCanUseFastCheckSelector : 0) | (viewportRuleIsProcessed ? ViewportRuleIsProcessed : 0));
 
     addChildRules(sheet->childRules(), medium, resolver, scope, hasDocumentSecurityOrigin, addRuleFlags);
 }