Add watch time metrics for HTML5 media playback.

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index 9fb661d1bfef88c57f73171bba0a1b74013bcd64..f12d951ce8eb8a280bd3643b4dbfbad6dd8476e0 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -72,6 +72,7 @@ class GpuVideoAcceleratorFactories;
 class MediaLog;
 class UrlIndex;
 class VideoFrameCompositor;
+class WatchTimeReporter;
 class WebAudioSourceProviderImpl;
 class WebMediaPlayerDelegate;
 class WebTextTrackImpl;
@@ -349,6 +350,8 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   // paused state after some idle timeout.
   void ScheduleIdlePauseTimer();
 
+  void CreateWatchTimeReporter();
+
   blink::WebLocalFrame* frame_;
 
   // The playback state last reported to |delegate_|, to avoid setting duplicate
@@ -535,6 +538,10 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   // state as part of the call to OnHidden().
   base::OneShotTimer background_pause_timer_;
 
+  // Monitors the watch time of the played content.
+  std::unique_ptr<WatchTimeReporter> watch_time_reporter_;
+  bool is_encrypted_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };