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 edee39b72ecd923944efcf8947280af47f12a26e..e1bc4ac41712092815b30cd4ff8fb7f07e24c2ba 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;
@@ -535,6 +536,10 @@ 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.
+  bool is_encrypted_;
+  std::unique_ptr<WatchTimeReporter> watch_time_reporter_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };