getUserMeida: report device starting states

content/browser/renderer_host/media/video_capture_controller_event_handler.h

Index: content/browser/renderer_host/media/video_capture_controller_event_handler.h
diff --git a/content/browser/renderer_host/media/video_capture_controller_event_handler.h b/content/browser/renderer_host/media/video_capture_controller_event_handler.h
index b8a8a82bdf3884d44b2a658c39ea15bac083008a..27f5bfdac615a6ac976bcf29ad6b3a2075f61d1f 100644
--- a/content/browser/renderer_host/media/video_capture_controller_event_handler.h
+++ b/content/browser/renderer_host/media/video_capture_controller_event_handler.h
@@ -23,6 +23,11 @@ typedef int VideoCaptureControllerID;
 // VideoCaptureControllerEventHandler is the interface for
 // VideoCaptureController to notify clients about the events such as
 // BufferReady, FrameInfo, Error, etc.
+
+// OnStarted can be forwarded directly, while OnError&OnEnded need to be
+// scheduled to the end of message queue to guarantee some other clearing
+// jobs are done before they are handled.

[chfremer, 2017/02/22 19:13:58]

directly -> synchronously (to use the more precise technical term)

Since we are specifying this for some of the methods, a reader will naturally
also want to know about the remaining methods OnBufferCreated,
OnBufferDestroyed, OnBufferReady?
Can they be forwarded synchronously?

[braveyao, 2017/02/23 00:06:26]

Done.

+
 // TODO(mcasas): https://crbug.com/654176 merge back into VideoCaptureController
 class CONTENT_EXPORT VideoCaptureControllerEventHandler {
  public:
@@ -47,6 +52,9 @@ class CONTENT_EXPORT VideoCaptureControllerEventHandler {
   // The capture session has ended and no more frames will be sent.
   virtual void OnEnded(VideoCaptureControllerID id) = 0;
 
+  // VideoCaptureDevice has successfully started the device.
+  virtual void OnStarted(VideoCaptureControllerID id) = 0;
+
  protected:
   virtual ~VideoCaptureControllerEventHandler() {}
 };