Remove the concept of user stylesheets.

Source/core/css/StyleRuleImport.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 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.
  *
@@ skipping 97 matching lines @@
     // in our parent chain with the same URL, then just bail.
     StyleSheetContents* rootSheet = m_parentStyleSheet;
     for (StyleSheetContents* sheet = m_parentStyleSheet; sheet; sheet = sheet->parentStyleSheet()) {
         if (equalIgnoringFragmentIdentifier(absURL, sheet->baseURL())
             || equalIgnoringFragmentIdentifier(absURL, document->completeURL(sheet->originalURL())))
             return;
         rootSheet = sheet;
     }
 
     FetchRequest request(ResourceRequest(absURL), FetchInitiatorTypeNames::css, m_parentStyleSheet->charset());
-    if (m_parentStyleSheet->isUserStyleSheet())
-        m_resource = fetcher->fetchUserCSSStyleSheet(request);
-    else
-        m_resource = fetcher->fetchCSSStyleSheet(request);
+    m_resource = fetcher->fetchCSSStyleSheet(request);
     if (m_resource) {
         // if the import rule is issued dynamically, the sheet may be
         // removed from the pending sheet count, so let the doc know
         // the sheet being imported is pending.
         if (m_parentStyleSheet && m_parentStyleSheet->loadCompleted() && rootSheet == m_parentStyleSheet)
             m_parentStyleSheet->startLoadingDynamicSheet();
         m_loading = true;
         m_resource->addClient(&m_styleSheetClient);
     }
 }
 
 } // namespace WebCore