getUserMeida: report device starting states

media/capture/video/win/video_capture_device_win.cc

 // Copyright (c) 2012 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.
 
 #include "media/capture/video/win/video_capture_device_win.h"
 
 #include <ks.h>
 #include <ksmedia.h>
 
 #include <algorithm>
@@ skipping 404 matching lines @@
     return;
   }
 
   // Start capturing.
   hr = media_control_->Run();
   if (FAILED(hr)) {
     SetErrorState(FROM_HERE, "Failed to start the Capture device.", hr);
     return;
   }
 
+  client_->OnStarted();
   state_ = kCapturing;
 }
 
 void VideoCaptureDeviceWin::StopAndDeAllocate() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (state_ != kCapturing)
     return;
 
   HRESULT hr = media_control_->Stop();
   if (FAILED(hr)) {
@@ skipping 15 matching lines @@
   // way, however, is not widespread and proves too cumbersome, so we just grab
   // the next captured frame instead.
   take_photo_callbacks_.push(std::move(callback));
 }
 
 // Implements SinkFilterObserver::SinkFilterObserver.
 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();
 
   // There is a chance that the platform does not provide us with the timestamp,
   // in which case, we use reference time to calculate a timestamp.
   if (timestamp == media::kNoTimestamp)
     timestamp = base::TimeTicks::Now() - first_ref_time_;
 
   client_->OnIncomingCapturedData(buffer, length, format, 0,
                                   base::TimeTicks::Now(), timestamp);
@@ skipping 119 matching lines @@
 void VideoCaptureDeviceWin::SetErrorState(
     const tracked_objects::Location& from_here,
     const std::string& reason,
     HRESULT hr) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DLOG_IF_FAILED_WITH_HRESULT(reason, hr);
   state_ = kError;
   client_->OnError(from_here, reason);
 }
 }  // namespace media