StyleResolver should update RuleSets lazily.

Source/core/inspector/InspectorCSSAgent.cpp

Index: Source/core/inspector/InspectorCSSAgent.cpp
diff --git a/Source/core/inspector/InspectorCSSAgent.cpp b/Source/core/inspector/InspectorCSSAgent.cpp
index 0ee38c8269753284a0176be40d35d5aebfd5aefd..5a9d6760151401fa924c6ff51eeb90bb20e4674f 100644
--- a/Source/core/inspector/InspectorCSSAgent.cpp
+++ b/Source/core/inspector/InspectorCSSAgent.cpp
@@ -918,6 +918,7 @@ void InspectorCSSAgent::getMatchedStylesForNode(ErrorString* errorString, int no
 
     // Matched rules.
     StyleResolver* styleResolver = element->ownerDocument()->styleResolver();
+    appendPendingStyleSheetsIfNeeded(styleResolver);
     // FIXME: This code should not pass DoNotIncludeStyleSheetInCSSOMWrapper. All CSSOMWrappers should always have a parent sheet or rule.
     RefPtr<CSSRuleList> matchedRules = styleResolver->pseudoCSSRulesForElement(element, elementPseudoId, StyleResolver::AllCSSRules, DoNotIncludeStyleSheetInCSSOMWrapper);
     matchedCSSRules = buildArrayForMatchedRuleList(matchedRules.get(), styleResolver, originalElement);
@@ -944,6 +945,7 @@ void InspectorCSSAgent::getMatchedStylesForNode(ErrorString* errorString, int no
         Element* parentElement = element->parentElement();
         while (parentElement) {
             StyleResolver* parentStyleResolver = parentElement->ownerDocument()->styleResolver();
+            appendPendingStyleSheetsIfNeeded(parentStyleResolver);
             RefPtr<CSSRuleList> parentMatchedRules = parentStyleResolver->cssRulesForElement(parentElement, StyleResolver::AllCSSRules, DoNotIncludeStyleSheetInCSSOMWrapper);
             RefPtr<TypeBuilder::CSS::InheritedStyleEntry> entry = TypeBuilder::CSS::InheritedStyleEntry::create()
                 .setMatchedCSSRules(buildArrayForMatchedRuleList(parentMatchedRules.get(), styleResolver, parentElement));
@@ -1070,6 +1072,7 @@ void InspectorCSSAgent::getStyleSheet(ErrorString* errorString, const String& st
     Document* doc = inspectorStyleSheet->pageStyleSheet() ? inspectorStyleSheet->pageStyleSheet()->ownerDocument() : 0;
     if (!doc || !doc->styleResolver())
         return;
+    appendPendingStyleSheetsIfNeeded(doc->styleResolver());
 
     RefPtr<TypeBuilder::CSS::CSSStyleSheetBody> result = TypeBuilder::CSS::CSSStyleSheetBody::create()
         .setStyleSheetId(styleSheetId)