media: Cleanup class/struct forward declarations

media/audio/clockless_audio_sink.h

 // Copyright 2013 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 MEDIA_AUDIO_CLOCKLESS_AUDIO_SINK_H_
 #define MEDIA_AUDIO_CLOCKLESS_AUDIO_SINK_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "media/base/audio_renderer_sink.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace media {
-class AudioBus;
 class ClocklessAudioSinkThread;
 
 // Implementation of an AudioRendererSink that consumes the audio as fast as
 // possible. This class does not support multiple Play()/Pause() events.
 class MEDIA_EXPORT ClocklessAudioSink
     : NON_EXPORTED_BASE(public AudioRendererSink) {
  public:
   ClocklessAudioSink();
   explicit ClocklessAudioSink(const OutputDeviceInfo& device_info);
 
@@ skipping 29 matching lines @@
 
   // Time taken in last set of Render() calls.
   base::TimeDelta playback_time_;
 
   DISALLOW_COPY_AND_ASSIGN(ClocklessAudioSink);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_CLOCKLESS_AUDIO_SINK_H_