Monitor the intersection of video and viewport.

third_party/WebKit/Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 516 matching lines @@
   void scheduleResolvePlayPromises();
   void scheduleRejectPlayPromises(ExceptionCode);
   void scheduleNotifyPlaying();
   void resolveScheduledPlayPromises();
   void rejectScheduledPlayPromises();
   void rejectPlayPromises(ExceptionCode, const String&);
   void rejectPlayPromisesInternal(ExceptionCode, const String&);
 
   EnumerationHistogram& showControlsHistogram() const;
 
-  void onVisibilityChangedForAutoplay(bool isVisible);
+  void onVideoViewportRatioChanged(bool isVisible);
 
   UnthrottledThreadTimer<HTMLMediaElement> m_loadTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_progressEventTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_playbackProgressTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_audioTracksTimer;
   Member<TimeRanges> m_playedTimeRanges;
   Member<GenericEventQueue> m_asyncEventQueue;
 
   double m_playbackRate;
   double m_defaultPlaybackRate;
@@ skipping 161 matching lines @@
 
   friend class AutoplayUmaHelper;  // for isAutoplayAllowedPerSettings
   friend class Internals;
   friend class TrackDisplayUpdateScope;
   friend class AutoplayExperimentHelper;
   friend class MediaControlsTest;
 
   Member<AutoplayExperimentHelper::Client> m_autoplayHelperClient;
   Member<AutoplayExperimentHelper> m_autoplayHelper;
   Member<AutoplayUmaHelper> m_autoplayUmaHelper;
+  bool m_autoplayWhenVisible = false;

[miu, 2016/11/05 02:47:47]

naming nit: m_shouldAutoplayWhenVisible

[miu, 2016/11/05 02:47:47]

Is the boolean necessary? (See comment in .cpp file.)

[xjz, 2016/11/09 02:24:28]

I keeps this boolean to save a bunch of checks every time when muted video
becomes visible: state change logic + tracksAreReady + shouldAutoplay() +
!isGestureNeededForPlayback() + isHTMLVideoElement() + muted() +
autoplayMutedVideosEnabled.

[xjz, 2016/11/09 02:24:28]

Done.

 
   WebRemotePlaybackClient* m_remotePlaybackClient;
 
-  // class AutoplayVisibilityObserver;
-  Member<ElementVisibilityObserver> m_autoplayVisibilityObserver;
+  Member<ElementVisibilityObserver> m_videoViewportRatioObserver;
 
   static URLRegistry* s_mediaStreamRegistry;
 };
 
 inline bool isHTMLMediaElement(const HTMLElement& element) {
   return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 }  // namespace blink
 
 #endif  // HTMLMediaElement_h