Split the constructor of ThreadableLoader into two methods (ctor and start())

Source/core/xmlhttprequest/XMLHttpRequest.cpp

 /*
  *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
  *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
  *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 915 matching lines @@
     }
 
     m_exceptionCode = 0;
     m_error = false;
 
     if (m_async) {
         UseCounter::count(&executionContext, UseCounter::XMLHttpRequestAsynchronous);
         if (m_upload)
             request.setReportUploadProgress(true);
 
-        // ThreadableLoader::create can return null here, for example if we're no longer attached to a page.
-        // This is true while running onunload handlers.
-        // FIXME: Maybe we need to be able to send XMLHttpRequests from onunload, <http://bugs.webkit.org/show_bug.cgi?id=10904>.
-        // FIXME: Maybe create() can return null for other reasons too?
         ASSERT(!m_loader);
-        m_loader = ThreadableLoader::create(executionContext, this, request, options, resourceLoaderOptions);
+        m_loader = ThreadableLoader::create(executionContext, this, options, resourceLoaderOptions);
+        m_loader->start(request);
 
         return;
     }
 
     // Use count for XHR synchronous requests.
     UseCounter::count(&executionContext, UseCounter::XMLHttpRequestSynchronous);
     ThreadableLoader::loadResourceSynchronously(executionContext, request, *this, options, resourceLoaderOptions);
 
     throwForLoadFailureIfNeeded(exceptionState, String());
 }
@@ skipping 741 matching lines @@
     visitor->trace(m_responseDocumentParser);
     visitor->trace(m_progressEventThrottle);
     visitor->trace(m_upload);
     visitor->trace(m_blobLoader);
     XMLHttpRequestEventTarget::trace(visitor);
     DocumentParserClient::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink