[chromecast] Simplify CastAudioOutputStream.

chromecast/media/audio/cast_audio_manager.h

 // Copyright 2015 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 CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_
 #define CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_
 
 #include "base/macros.h"
 #include "media/audio/audio_manager_base.h"
 
@@ skipping 17 matching lines @@
 
   // AudioManager implementation.
   bool HasAudioOutputDevices() override;
   bool HasAudioInputDevices() override;
   void ShowAudioInputSettings() override;
   void GetAudioInputDeviceNames(
       ::media::AudioDeviceNames* device_names) override;
   ::media::AudioParameters GetInputStreamParameters(
       const std::string& device_id) override;
 
-  // This must be called on cast media thread.
-  // See chromecast::media::MediaMessageLoop.
+  // This must be called on audio thread.
   virtual std::unique_ptr<MediaPipelineBackend> CreateMediaPipelineBackend(
       const MediaPipelineDeviceParams& params);
 
  protected:
   ~CastAudioManager() override;
 
  private:
   // AudioManagerBase implementation.
   ::media::AudioOutputStream* MakeLinearOutputStream(
       const ::media::AudioParameters& params) override;
@@ skipping 12 matching lines @@
 
   MediaPipelineBackendManager* const backend_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(CastAudioManager);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_