Pass camera facing info to audio client

media/base/video_facing.h

 // Copyright 2017 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_BASE_VIDEO_FACING_H_
 #define MEDIA_BASE_VIDEO_FACING_H_
 
+#if defined(OS_CHROMEOS)
+#include "chromeos/audio/cras_audio_handler.h"
+#endif
+
 namespace media {
 
 // Facing mode for video capture.
 enum VideoFacingMode {
   MEDIA_VIDEO_FACING_NONE = 0,
   MEDIA_VIDEO_FACING_USER,
   MEDIA_VIDEO_FACING_ENVIRONMENT,
 
   NUM_MEDIA_VIDEO_FACING_MODE
 };
 
+class VideoCaptureObserver {
+ public:
+  virtual void OnVideoCaptureStarted(VideoFacingMode facing) = 0;
+  virtual void OnVideoCaptureStopped(VideoFacingMode facing) = 0;
+};
+
+class VideoCaptureObserverAdapter : public VideoCaptureObserver {

[chfremer, 2017/01/30 19:49:28]

The way this looks to me now is that VideoCaptureObserverAdapter is a
chromeos-specific implementation of media::VideoCaptureObserver. 

As such, it would make sense to move the chromeos specific parts to a separate
file that is only built for chromeos builds. This way we could avoid the #if
defined(OS_CHROMEOS) in the platform-independent layer of the code. And then we
could call this class ChromeOSVideoCaptureObserver, which would make it more
clear that the dependency of media on chromeos serves the purpose of providing a
chromeos-specific implementation of a platform-independent media interface.

[shenghao, 2017/02/08 02:07:10]

I name it to be VideoCaptureObserverChromeOS. The convention is to put ChromeOS
as the suffix.

+ public:
+#if defined(OS_CHROMEOS)
+  VideoCaptureObserverAdapter(chromeos::VideoCaptureObserver* observer);
+#endif
+  VideoCaptureObserverAdapter();
+  void OnVideoCaptureStarted(VideoFacingMode facing) override;
+  void OnVideoCaptureStopped(VideoFacingMode facing) override;
+
+#if defined(OS_CHROMEOS)
+ private:
+  chromeos::VideoCaptureObserver* const observer_;
+#endif
+};
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_FACING_H_