content: Cleanup class/struct forward declarations

content/renderer/media/media_stream_audio_processor.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 CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_PROCESSOR_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_PROCESSOR_H_
 
 #include "base/atomicops.h"
 #include "base/files/file.h"
 #include "base/gtest_prod_util.h"
@@ skipping 21 matching lines @@
 #define ENABLE_AUDIO_REPETITION_DETECTOR 0
 #endif
 #endif
 
 namespace blink {
 class WebMediaConstraints;
 }
 
 namespace media {
 class AudioBus;
-class AudioFifo;
 class AudioParameters;
 }  // namespace media
 
 namespace webrtc {
 class TypingDetection;
 }
 
 namespace content {
 
 class EchoInformation;
@@ skipping 186 matching lines @@
   // Object for logging UMA stats for echo information when the AEC is enabled.
   // Accessed on the main render thread.
   std::unique_ptr<EchoInformation> echo_information_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamAudioProcessor);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_PROCESSOR_H_