Refactor the API for setting dynamic resource load priorities

Source/core/fetch/ResourceClient.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Library General Public License for more details.
 
     You should have received a copy of the GNU Library General Public License
     along with this library; see the file COPYING.LIB.  If not, write to
     the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
 
     This class provides all functionality needed for loading images, style sheets and html
     pages from the web. It has a memory cache for these objects.
 */
 
 #ifndef ResourceClient_h
 #define ResourceClient_h
 
 #include "core/CoreExport.h"
+#include "platform/network/ResourceLoadPriority.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 class Resource;
 
 class CORE_EXPORT ResourceClient {
 public:
     enum ResourceClientType {
         BaseResourceType,
         ImageType,
         FontType,
         StyleSheetType,
         DocumentType,
         RawResourceType,
         ScriptType
     };
 
     virtual ~ResourceClient() { }
     virtual void notifyFinished(Resource*) { }
 
     static ResourceClientType expectedType() { return BaseResourceType; }
     virtual ResourceClientType resourceClientType() const { return expectedType(); }
 
+    virtual ResourcePriority updatePriority(Resource*) { return ResourcePriority(); }
+
 protected:
     ResourceClient() { }
 };
 }
 
 #endif