Pass camera facing info to audio client

media/base/video_facing.h

Index: media/base/video_facing.h
diff --git a/media/base/video_facing.h b/media/base/video_facing.h
index 9bd0b50e0a52421c1bc14af77c02d9a3f83c534d..bf354c2a70c40e16b9b26f358606695ec6527261 100644
--- a/media/base/video_facing.h
+++ b/media/base/video_facing.h
@@ -13,7 +13,16 @@ enum VideoFacingMode {
   MEDIA_VIDEO_FACING_USER,
   MEDIA_VIDEO_FACING_ENVIRONMENT,
 
-  NUM_MEDIA_VIDEO_FACING_MODE
+  NUM_MEDIA_VIDEO_FACING_MODES
+};
+
+// Clients interested in video capture events can implement this interface
+// and register the observers to MediaStreamManager or VideoCaptureManager.
+class VideoCaptureObserver {
+ public:
+  virtual ~VideoCaptureObserver() {}
+  virtual void OnVideoCaptureStarted(VideoFacingMode facing) = 0;
+  virtual void OnVideoCaptureStopped(VideoFacingMode facing) = 0;
 };
 
 }  // namespace media