Split out const/non-const variants of Resource::resourceRequest().

Source/core/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     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
@@ skipping 733 matching lines @@
 
     if (!resource->hasClients())
         m_deadStatsRecorder.update(policy);
 
     if (policy != Use)
         resource->setIdentifier(createUniqueIdentifier());
 
     if (!request.forPreload() || policy != Use) {
         ResourceLoadPriority priority = loadPriority(type, request);
         if (priority != resource->resourceRequest().priority()) {
-            resource->resourceRequest().setPriority(priority);
+            resource->mutableResourceRequest().setPriority(priority);
             resource->didChangePriority(priority, 0);
         }
     }
 
     if (resourceNeedsLoad(resource.get(), request, policy)) {
         if (!shouldLoadNewResource(type)) {
             if (memoryCache()->contains(resource.get()))
                 memoryCache()->remove(resource.get());
             return 0;
         }
@@ skipping 772 matching lines @@
     }
 }
 
 void ResourceFetcher::trace(Visitor* visitor)
 {
     visitor->trace(m_document);
     ResourceLoaderHost::trace(visitor);
 }
 
 }