Optimize StyleSheetContents::checkLoaded by keeping track of completed

Source/core/css/CSSStyleSheet.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 111 matching lines @@
     CSSStyleSheet(PassRefPtrWillBeRawPtr<StyleSheetContents>, CSSImportRule* ownerRule);
     CSSStyleSheet(PassRefPtrWillBeRawPtr<StyleSheetContents>, Node* ownerNode, bool isInlineStylesheet, const TextPosition& startPosition);
 
     virtual bool isCSSStyleSheet() const OVERRIDE { return true; }
     virtual String type() const OVERRIDE { return "text/css"; }
 
     void reattachChildRuleCSSOMWrappers();
 
     bool canAccessRules() const;
 
+    void setLoadCompleted(bool);
+
     RefPtrWillBeMember<StyleSheetContents> m_contents;
     bool m_isInlineStylesheet;
     bool m_isDisabled;
     String m_title;
     RefPtrWillBeMember<MediaQuerySet> m_mediaQueries;
 
     Node* m_ownerNode;
     RawPtrWillBeMember<CSSRule> m_ownerRule;
 
     TextPosition m_startPosition;
@@ skipping 21 matching lines @@
 {
     if (m_styleSheet)
         m_styleSheet->didMutateRules();
 }
 
 DEFINE_TYPE_CASTS(CSSStyleSheet, StyleSheet, sheet, sheet->isCSSStyleSheet(), sheet.isCSSStyleSheet());
 
 } // namespace
 
 #endif