Detect change on the intersection of video and viewport.

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

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
index 0bd98bca6d30fa8ac49f065ddad4b715583cedbb..7cb0191de3219981bdb2df9fd06f1d353cb0b359 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -544,10 +544,14 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
 
   void onVisibilityChangedForAutoplay(bool isVisible);
 
+  void checkViewportIntersectionChanged();
+  void viewportFillDebouncerTimerFired(TimerBase*);
+
   UnthrottledThreadTimer<HTMLMediaElement> m_loadTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_progressEventTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_playbackProgressTimer;
   UnthrottledThreadTimer<HTMLMediaElement> m_audioTracksTimer;
+  UnthrottledThreadTimer<HTMLMediaElement> m_viewportFillDebouncerTimer;
   Member<TimeRanges> m_playedTimeRanges;
   Member<GenericEventQueue> m_asyncEventQueue;
 
@@ -731,6 +735,9 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
   // class AutoplayVisibilityObserver;
   Member<ElementVisibilityObserver> m_autoplayVisibilityObserver;
 
+  IntRect m_currentIntersectRect;
+  bool m_mostlyFillingViewport = false;

[ojan, 2016/11/24 00:48:33]

Put the bool up in line 653 instead with the ": 1" syntax so that it can tightly
pack with the other bools. Otherwise, this line will use 32-64 bits of memory
instead of 1. :)

[xjz, 2016/11/24 02:16:16]

Done.

+
   static URLRegistry* s_mediaStreamRegistry;
 };