URLFetcher uses a TaskRunner instead of a message loop.

net/url_request/test_url_fetcher_factory.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_URL_REQUEST_TEST_URL_FETCHER_FACTORY_H_
 #define NET_URL_REQUEST_TEST_URL_FETCHER_FACTORY_H_
 
 #include <list>
 #include <map>
 #include <string>
@@ skipping 92 matching lines @@
   virtual void SetURLRequestUserData(
       const void* key,
       const CreateDataCallback& create_data_callback) OVERRIDE;
   virtual void SetStopOnRedirect(bool stop_on_redirect) OVERRIDE;
   virtual void SetAutomaticallyRetryOn5xx(bool retry) OVERRIDE;
   virtual void SetMaxRetries(int max_retries) OVERRIDE;
   virtual int GetMaxRetries() const OVERRIDE;
   virtual base::TimeDelta GetBackoffDelay() const OVERRIDE;
   virtual void SaveResponseToFileAtPath(
       const FilePath& file_path,
-      scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy) OVERRIDE;
+      scoped_refptr<base::TaskRunner> file_task_runner) OVERRIDE;
   virtual void SaveResponseToTemporaryFile(
-      scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy) OVERRIDE;
+      scoped_refptr<base::TaskRunner> file_task_runner) OVERRIDE;
   virtual HttpResponseHeaders* GetResponseHeaders() const OVERRIDE;
   virtual HostPortPair GetSocketAddress() const OVERRIDE;
   virtual bool WasFetchedViaProxy() const OVERRIDE;
   virtual void Start() OVERRIDE;
 
   // URL we were created with. Because of how we're using URLFetcher GetURL()
   // always returns an empty URL. Chances are you'll want to use
   // GetOriginalURL() in your tests.
   virtual const GURL& GetOriginalURL() const OVERRIDE;
   virtual const GURL& GetURL() const OVERRIDE;
@@ skipping 188 matching lines @@
       int id,
       const GURL& url,
       URLFetcher::RequestType request_type,
       URLFetcherDelegate* d) OVERRIDE;
 
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_TEST_URL_FETCHER_FACTORY_H_