media: Cleanup class/struct forward declarations

media/audio/virtual_audio_sink.h

 // 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.
 
 #ifndef MEDIA_AUDIO_VIRTUAL_AUDIO_SINK_H_
 #define MEDIA_AUDIO_VIRTUAL_AUDIO_SINK_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_source_diverter.h"
 #include "media/base/audio_converter.h"
 #include "media/base/audio_shifter.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace media {
 
 class VirtualAudioInputStream;
 
 // This class is an adapter between push model and pull model for audio stream.
 // This class is thread safe.
 // Audio provider calls OnData() to push audio data into this class.
 // Audio consumer calls ProvideInput() to pull audio data.
 class MEDIA_EXPORT VirtualAudioSink : public AudioPushSink,
                                       public AudioConverter::InputCallback {
@@ skipping 23 matching lines @@
   AudioShifter shifter_;
   base::Lock shifter_lock_;
   AfterCloseCallback after_close_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(VirtualAudioSink);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_VIRTUAL_AUDIO_SINK_H_