StyleResolver should update RuleSets lazily.

Source/core/frame/DOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1324 matching lines @@
     CSSSelector::PseudoType pseudoType = CSSSelector::parsePseudoType(AtomicString(pseudoElement.substring(colonStart)));
     if (pseudoType == CSSSelector::PseudoUnknown && !pseudoElement.isEmpty())
         return 0;
 
     unsigned rulesToInclude = StyleResolver::AuthorCSSRules;
     if (!authorOnly)
         rulesToInclude |= StyleResolver::UAAndUserCSSRules;
 
     PseudoId pseudoId = CSSSelector::pseudoId(pseudoType);
 
-    return m_frame->document()->styleResolver()->pseudoCSSRulesForElement(element, pseudoId, rulesToInclude);
+    StyleResolver* styleResolver = m_frame->document()->styleResolver();
+    appendPendingStyleSheetsIfNeeded(styleResolver);
+    return styleResolver->pseudoCSSRulesForElement(element, pseudoId, rulesToInclude);
 }
 
 PassRefPtr<DOMPoint> DOMWindow::webkitConvertPointFromNodeToPage(Node* node, const DOMPoint* p) const
 {
     if (!node || !p)
         return 0;
 
     if (!document())
         return 0;
 
@@ skipping 512 matching lines @@
     return static_cast<DOMWindowLifecycleNotifier&>(LifecycleContext::lifecycleNotifier());
 }
 
 PassOwnPtr<LifecycleNotifier<DOMWindow> > DOMWindow::createLifecycleNotifier()
 {
     return DOMWindowLifecycleNotifier::create(this);
 }
 
 
 } // namespace WebCore