Add 'XHR' to the Resource::Type enum, and use it for XHR requests.

Source/core/loader/DocumentThreadableLoader.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013, Intel Corporation
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 408 matching lines @@
             resourceLoaderOptions.dataBufferingPolicy = BufferData;
         }
 
         if (m_options.timeoutMilliseconds > 0)
             m_timeoutTimer.startOneShot(m_options.timeoutMilliseconds / 1000.0, FROM_HERE);
 
         FetchRequest newRequest(request, m_options.initiator, resourceLoaderOptions);
         ASSERT(!resource());
         if (request.targetType() == ResourceRequest::TargetIsMedia)
             setResource(m_document.fetcher()->fetchMedia(newRequest));
+        else if (request.targetType() == ResourceRequest::TargetIsXHR)
+            setResource(m_document.fetcher()->fetchXMLHttpRequest(newRequest));
         else
             setResource(m_document.fetcher()->fetchRawResource(newRequest));
         if (resource() && resource()->loader()) {
             unsigned long identifier = resource()->identifier();
             InspectorInstrumentation::documentThreadableLoaderStartedLoadingForClient(&m_document, identifier, m_client);
         }
         return;
     }
 
     FetchRequest fetchRequest(request, m_options.initiator, resourceLoaderOptions);
@@ skipping 54 matching lines @@
         return DoNotAllowStoredCredentials;
     return m_resourceLoaderOptions.allowCredentials;
 }
 
 SecurityOrigin* DocumentThreadableLoader::securityOrigin() const
 {
     return m_securityOrigin ? m_securityOrigin.get() : m_document.securityOrigin();
 }
 
 } // namespace WebCore