media: Cleanup class/struct forward declarations

media/audio/sounds/audio_stream_handler.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_SOUNDS_AUDIO_STREAM_HANDLER_H_
 #define MEDIA_AUDIO_SOUNDS_AUDIO_STREAM_HANDLER_H_
 
 #include <stddef.h>
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/strings/string_piece.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/time/time.h"
 #include "media/audio/audio_io.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
-class AudioManager;
-
 // This class sends a sound to the audio manager.
 class MEDIA_EXPORT AudioStreamHandler : public base::NonThreadSafe {
  public:
   class TestObserver {
    public:
     virtual ~TestObserver() {}
 
     // Following methods will be called only from the audio thread.
 
     // Called when AudioOutputStreamProxy::Start() was successfully called.
@@ skipping 37 matching lines @@
 
   base::TimeDelta duration_;
   std::unique_ptr<AudioStreamContainer> stream_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioStreamHandler);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_SOUNDS_AUDIO_STREAM_HANDLER_H_