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

media/blink/webmediaplayer_impl.h

 // 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.
 
 #ifndef MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_
 #define MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 233 matching lines @@
     bool is_suspended;
   };
 
  private:
   friend class WebMediaPlayerImplTest;
 
   void EnableOverlay();
   void DisableOverlay();
 
   void OnPipelineSuspended();
+  void OnBeforePipelineResume();
+  void OnPipelineResumed();
   void OnDemuxerOpened();
 
   // Pipeline::Client overrides.
   void OnError(PipelineStatus status) override;
   void OnEnded() override;
   void OnMetadata(PipelineMetadata metadata) override;
   void OnBufferingStateChange(BufferingState state) override;
   void OnDurationChange() override;
   void OnAddTextTrack(const TextTrackConfig& config,
                       const AddTextTrackDoneCB& done_cb) override;
@@ skipping 103 matching lines @@
   // Returns true if the player's source is streaming.
   bool IsStreaming() const;
 
   // Return whether |pipeline_metadata_| is compatible with an overlay. This
   // is intended for android.
   bool DoesOverlaySupportMetadata() const;
 
   // Whether the media should be paused when hidden.
   bool ShouldPauseWhenHidden() const;
 
+  // Whether the video track should be disabled when hidden.
+  bool ShouldDisableVideoWhenHidden() const;
+
+  // Disables the video track to save power if possible.
+  // Must be called when the video was hidden and also when pipeline seeked or
+  // resumed if the video is hidden.
+  void DisableVideoTrackIfNeeded();
+
+  // Enables the video track if it was disabled before to save power,
+  // if possible.
+  // Must be called when the video was shown and also when pipeline seeked or
+  // resumed if the video is shown.
+  // Must also be called when the pipeline is about to resume, see
+  // https://crbug.com/678374.

[sandersd (OOO until July 31), 2017/01/10 21:34:37]

Somewhat confusing, in particular because resume is listed twice.

It's also not true that (as I understand it) to add the track back for a seek;
only for start (but please comment that |seeking_| is used as a proxy for
starting).

It's probably true that we don't want to change the active tracks during a seek,
so I won't recommend changing to testing for 'starting' explicitly. (But if you
do want it to be more explicit, you can rename and set |is_pipeline_resuming_|
during startup.)

[whywhat, 2017/01/11 19:41:30]

Rephrased the comments, hopefully they are less confusing now.

+  void EnableVideoTrackIfNeeded();
+
   blink::WebLocalFrame* frame_;
 
   // The playback state last reported to |delegate_|, to avoid setting duplicate
   // states. (Which can have undesired effects like resetting the idle timer.)
   DelegateState delegate_state_;
 
   // Set when OnSuspendRequested() is called with |must_suspend| unset.
   bool is_idle_;
 
   // Set when OnSuspendRequested() is called with |must_suspend| set.
@@ skipping 208 matching lines @@
   base::TimeTicks last_time_loading_progressed_;
 
   std::unique_ptr<base::TickClock> tick_clock_;
 
   // Monitors the player events.
   base::WeakPtr<MediaObserver> observer_;
 
   // 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);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_