StyleResolver should update RuleSets lazily.

Source/core/dom/StyleEngine.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 381 matching lines @@
             ASSERT(collection);
             collection->updateActiveStyleSheets(this, updateMode);
             if (!collection->hasStyleSheetCandidateNodes())
                 treeScopesRemoved.add(treeScope);
         }
         if (!treeScopesRemoved.isEmpty())
             for (HashSet<TreeScope*>::iterator it = treeScopesRemoved.begin(); it != treeScopesRemoved.end(); ++it)
                 m_activeTreeScopes.remove(*it);
         m_dirtyTreeScopes.clear();
     }
-
-    if (StyleResolver* styleResolver = m_document.styleResolverIfExists()) {
-        styleResolver->finishAppendAuthorStyleSheets();
-        resetCSSFeatureFlags(styleResolver->ruleFeatureSet());
-    }
-
     m_needsUpdateActiveStylesheetsOnStyleRecalc = false;
     activeStyleSheetsUpdatedForInspector();
     m_usesRemUnits = m_documentStyleSheetCollection.usesRemUnits();
 
     if (m_needsDocumentStyleSheetsUpdate || updateMode == FullStyleUpdate) {
         m_document.notifySeamlessChildDocumentsOfStylesheetUpdate();
         m_needsDocumentStyleSheetsUpdate = false;
     }
 
     return requiresFullStyleRecalc;
@@ skipping 40 matching lines @@
         if (StyleSheetCollection* collection = m_styleSheetCollectionMap.get(*it)) {
             styleResolver->setBuildScopedStyleTreeInDocumentOrder(!collection->scopingNodesForStyleScoped());
             styleResolver->appendAuthorStyleSheets(0, collection->activeAuthorStyleSheets());
         }
     }
     styleResolver->finishAppendAuthorStyleSheets();
     styleResolver->setBuildScopedStyleTreeInDocumentOrder(false);
 }
 
 }