extensions: Cleanup class/struct fwd declarations

extensions/renderer/api/display_source/wifi_display/wifi_display_media_pipeline.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 EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_PIPELINE_H_
 #define EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_PIPELINE_H_
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "extensions/common/mojo/wifi_display_session_service.mojom.h"
 #include "extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h"
 #include "extensions/renderer/api/display_source/wifi_display/wifi_display_media_packetizer.h"
 #include "extensions/renderer/api/display_source/wifi_display/wifi_display_video_encoder.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
 #include "third_party/wds/src/libwds/public/media_manager.h"
 
-namespace media {
-class AudioBus;
-}  // namespace media
-
 namespace extensions {
 
 // This class encapsulates the WiFi Display media pipeline including
 // - encoding
 // - AV multiplexing/packetization
 // - sending
 // Threading: should belong to IO thread.
 class WiFiDisplayMediaPipeline {
  public:
   using ErrorCallback = base::Callback<void(const std::string&)>;
@@ skipping 68 matching lines @@
   mojom::WiFiDisplayMediaServicePtr media_service_;
 
   base::WeakPtrFactory<WiFiDisplayMediaPipeline> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WiFiDisplayMediaPipeline);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_PIPELINE_H_