media: Cleanup class/struct forward declarations

media/audio/fake_audio_worker.h

 // Copyright (c) 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_FAKE_AUDIO_WORKER_H_
 #define MEDIA_AUDIO_FAKE_AUDIO_WORKER_H_
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/media_export.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
-class AudioBus;
 class AudioParameters;
 
 // A fake audio worker.  Using a provided message loop, FakeAudioWorker will
 // call back the provided callback like a real audio consumer or producer would.
 class MEDIA_EXPORT FakeAudioWorker {
  public:
   // |worker_task_runner| is the task runner on which the closure provided to
   // Start() will be executed on.  This may or may not be the be for the same
   // thread that invokes the Start/Stop methods.
   // |params| is used to determine the frequency of callbacks.
@@ skipping 17 matching lines @@
   // after the call to Stop() (on the main thread) returns.
   class Worker;
   const scoped_refptr<Worker> worker_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeAudioWorker);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_FAKE_AUDIO_WORKER_H_