[Media, Video] Enable the video track for a new renderer.

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 57d9f12effbc848f1356d88f8368644adf245401..274381c4dab02947fc8b3e4afca378c99eae7629 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -249,6 +249,8 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   void DisableOverlay();
 
   void OnPipelineSuspended();
+  void OnBeforePipelineResume();
+  void OnPipelineResumed();
   void OnDemuxerOpened();
 
   // Pipeline::Client overrides.
@@ -369,9 +371,30 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   // is intended for android.
   bool DoesOverlaySupportMetadata() const;
 
-  // Whether the media should be paused when hidden.
+  // Whether the media should be paused when hidden. Uses metadata so has
+  // meaning only after the pipeline has started, otherwise returns false.
   bool ShouldPauseWhenHidden() const;
 
+  // Whether the video track should be disabled when hidden. Uses metadata so
+  // has meaning only after the pipeline has started, otherwise returns false.
+  bool ShouldDisableVideoWhenHidden() const;
+
+  // Disables the video track to save power if possible.
+  // Must be called when either of the following happens:
+  // - right after the video was hidden,
+  // - right after the pipeline has started (|seeking_| is used to detect the
+  //   when pipeline started) if the video is hidden,
+  // - right ater the pipeline has resumed if the video is hidden.
+  void DisableVideoTrackIfNeeded();
+
+  // Enables the video track if it was disabled before to save power.
+  // Must be called when either of the following happens:
+  // - right after the video was shown,
+  // - right before the pipeline is requested to resume
+  //   (see https://crbug.com/678374),
+  // - right after the pipeline has resumed if the video is not hidden.
+  void EnableVideoTrackIfNeeded();
+
   blink::WebLocalFrame* frame_;
 
   // The playback state last reported to |delegate_|, to avoid setting duplicate
@@ -600,6 +623,12 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   // Whether the player is currently in autoplay muted state.
   bool autoplay_muted_ = false;
 
+  // Whether disabled the video track as an optimization.
+  bool video_track_disabled_ = false;
+
+  // Whether the pipeline is being resumed at the moment.
+  bool is_pipeline_resuming_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };