Remove all remaining traces of MessageLoopProxy.

blimp/engine/app/blimp_system_url_request_context_getter.cc

 // Copyright 2016 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.
 
 #include "blimp/engine/app/blimp_system_url_request_context_getter.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 24 matching lines @@
     // user request context getter. http://crbug/609981
     builder.set_proxy_service(net::ProxyService::CreateDirect());
     builder.set_user_agent(GetBlimpEngineUserAgent());
     url_request_context_ = builder.Build();
   }
   return url_request_context_.get();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 BlimpSystemURLRequestContextGetter::GetNetworkTaskRunner() const {
-  return content::BrowserThread::GetMessageLoopProxyForThread(
+  return content::BrowserThread::GetTaskRunnerForThread(
       content::BrowserThread::IO);
 }
 
 }  // namespace engine
 }  // namespace blimp