Remove the concept of user stylesheets.

Source/core/css/StyleSheetContents.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 68 matching lines @@
     Document* singleOwnerDocument() const;
 
     const String& charset() const { return m_parserContext.charset; }
 
     bool loadCompleted() const { return m_loadCompleted; }
     bool hasFailedOrCanceledSubresources() const;
 
     KURL completeURL(const String& url) const;
     void addSubresourceStyleURLs(ListHashSet<KURL>&);
 
-    void setIsUserStyleSheet(bool b) { m_isUserStyleSheet = b; }
-    bool isUserStyleSheet() const { return m_isUserStyleSheet; }
     void setHasSyntacticallyValidCSSHeader(bool b) { m_hasSyntacticallyValidCSSHeader = b; }
     bool hasSyntacticallyValidCSSHeader() const { return m_hasSyntacticallyValidCSSHeader; }
 
     void parserAddNamespace(const AtomicString& prefix, const AtomicString& uri);
     void parserAppendRule(PassRefPtr<StyleRuleBase>);
     void parserSetEncodingFromCharsetRule(const String& encoding);
     void parserSetUsesRemUnits(bool b) { m_usesRemUnits = b; }
 
     void clearRules();
 
@@ skipping 50 matching lines @@
 
     String m_originalURL;
 
     String m_encodingFromCharsetRule;
     Vector<RefPtr<StyleRuleImport> > m_importRules;
     Vector<RefPtr<StyleRuleBase> > m_childRules;
     typedef HashMap<AtomicString, AtomicString> PrefixNamespaceURIMap;
     PrefixNamespaceURIMap m_namespaces;
 
     bool m_loadCompleted : 1;
-    bool m_isUserStyleSheet : 1;
     bool m_hasSyntacticallyValidCSSHeader : 1;
     bool m_didLoadErrorOccur : 1;
     bool m_usesRemUnits : 1;
     bool m_isMutable : 1;
     bool m_isInMemoryCache : 1;
 
     CSSParserContext m_parserContext;
 
     Vector<CSSStyleSheet*> m_clients;
 };
 
 } // namespace
 
 #endif