[Media] Record time it takes to start rendering audio and video

media/blink/webmediaplayer_impl.cc

 // Copyright 2013 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/blink/webmediaplayer_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <string>
@@ skipping 1322 matching lines @@
   // Schedule suspended playing media to be paused if the user doesn't come back
   // to it within some timeout period to avoid any autoplay surprises.
   ScheduleIdlePauseTimer();
 }
 
 void WebMediaPlayerImpl::OnShown() {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
   if (watch_time_reporter_)
     watch_time_reporter_->OnShown();
 
+  compositor_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&VideoFrameCompositor::SetShownTimestamp,
+                 base::Unretained(compositor_), base::TimeTicks::Now()));
+
   if (IsBackgroundVideoTrackOptimizationEnabled() &&
       client_->hasSelectedVideoTrack()) {
     WebMediaPlayer::TrackId trackId = client_->getSelectedVideoTrackId();
     selectedVideoTrackChanged(&trackId);
   }
 
   must_suspend_ = false;
   background_pause_timer_.Stop();
 
   UpdatePlayState();
@@ skipping 658 matching lines @@
   return delegate_ && delegate_->IsHidden();
 }
 
 void WebMediaPlayerImpl::ActivateViewportIntersectionMonitoring(bool activate) {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
 
   client_->activateViewportIntersectionMonitoring(activate);
 }
 
 }  // namespace media