[chromecast] Simplify CastAudioOutputStream.

chromecast/media/audio/cast_audio_output_stream.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_OUTPUT_STREAM_H_
 #define CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_OUTPUT_STREAM_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "media/audio/audio_io.h"
 #include "media/base/audio_parameters.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}  // namespace base
-
 namespace chromecast {
 namespace media {
 
 class CastAudioManager;
 class DecoderBufferBase;
 
 class CastAudioOutputStream : public ::media::AudioOutputStream {
  public:
   CastAudioOutputStream(const ::media::AudioParameters& audio_params,
                         CastAudioManager* audio_manager);
   ~CastAudioOutputStream() override;
 
   // ::media::AudioOutputStream implementation.
   bool Open() override;
   void Close() override;
   void Start(AudioSourceCallback* source_callback) override;
   void Stop() override;
   void SetVolume(double volume) override;
   void GetVolume(double* volume) override;
 
  private:
   class Backend;
 
-  void OnClosed();
   void PushBuffer();
   void OnPushBufferComplete(bool success);
 
   const ::media::AudioParameters audio_params_;
   CastAudioManager* const audio_manager_;
 
   double volume_;
   AudioSourceCallback* source_callback_;
   std::unique_ptr<::media::AudioBus> audio_bus_;
   scoped_refptr<media::DecoderBufferBase> decoder_buffer_;
   std::unique_ptr<Backend> backend_;
   const base::TimeDelta buffer_duration_;
   bool push_in_progress_;
   base::TimeTicks next_push_time_;
 
-  scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner_;
-  scoped_refptr<base::SingleThreadTaskRunner> backend_task_runner_;
-
   base::WeakPtrFactory<CastAudioOutputStream> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CastAudioOutputStream);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_OUTPUT_STREAM_H_