Remove all remaining traces of MessageLoopProxy.

chrome/renderer/media/cast_threads.cc

 // Copyright 2014 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 "chrome/renderer/media/cast_threads.h"
 
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
 
 CastThreads::CastThreads()
     : audio_encode_thread_("CastAudioEncodeThread"),
       video_encode_thread_("CastVideoEncodeThread") {
   audio_encode_thread_.Start();
   video_encode_thread_.Start();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
-CastThreads::GetAudioEncodeMessageLoopProxy() {
+CastThreads::GetAudioEncodeTaskRunner() {
   return audio_encode_thread_.task_runner();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
-CastThreads::GetVideoEncodeMessageLoopProxy() {
+CastThreads::GetVideoEncodeTaskRunner() {
   return video_encode_thread_.task_runner();
 }