getUserMeida: report device starting states

media/capture/video/win/video_capture_device_win.cc

Index: media/capture/video/win/video_capture_device_win.cc
diff --git a/media/capture/video/win/video_capture_device_win.cc b/media/capture/video/win/video_capture_device_win.cc
index 4cb7f30c344e73282d949ab833f7117de2da645d..85e37df6fdc95e1c98fa40a772319433b7b07743 100644
--- a/media/capture/video/win/video_capture_device_win.cc
+++ b/media/capture/video/win/video_capture_device_win.cc
@@ -422,6 +422,7 @@ void VideoCaptureDeviceWin::AllocateAndStart(
     return;
   }
 
+  client_->OnStarted();
   state_ = kCapturing;
 }
 
@@ -457,6 +458,9 @@ void VideoCaptureDeviceWin::FrameReceived(const uint8_t* buffer,
                                           int length,
                                           const VideoCaptureFormat& format,
                                           base::TimeDelta timestamp) {
+  if (state_ != kCapturing)

[chfremer, 2017/02/17 23:51:15]

Unless this runs on the same thread as AllocateAndStart(), this check may happen
concurrently with AllocateAndStart() changing |state_| to kCapturing. I don't
know if this is a legal atomic operation or if it needs to be synchronized using
locks. Could you please check/confirm?

[braveyao, 2017/02/22 18:06:44]

Done.

+    return;
+
   if (first_ref_time_.is_null())
     first_ref_time_ = base::TimeTicks::Now();