Let AutoplayUmaHelper listen to visibilitychange instead of unload

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

 // Copyright 2016 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 AutoplayUmaHelper_h
 #define AutoplayUmaHelper_h
 
 #include "core/events/EventListener.h"
 #include "platform/heap/Handle.h"
 
@@ skipping 49 matching lines @@
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   explicit AutoplayUmaHelper(HTMLMediaElement*);
 
   void handleEvent(ExecutionContext*, Event*) override;
 
   void handlePlayingEvent();
   void handlePauseEvent();
-  void handleUnloadEvent();
+  void handlePageVisibilityChangeEvent();
 
-  void maybeUnregisterUnloadListener();
+  void maybeUnregisterPageVisibilityChangeListener();
 
   void maybeStartRecordingMutedVideoPlayMethodBecomeVisible();
   void maybeStopRecordingMutedVideoPlayMethodBecomeVisible(bool isVisible);
 
   void maybeStartRecordingMutedVideoOffscreenDuration();
   void maybeStopRecordingMutedVideoOffscreenDuration();
 
   void onVisibilityChangedForMutedVideoOffscreenDuration(bool isVisibile);
   void onVisibilityChangedForMutedVideoPlayMethodBecomeVisible(bool isVisible);
 
-  bool shouldListenToUnloadEvent() const;
+  bool shouldListenToPageVisibilityChangeEvent() const;
 
   // The autoplay source. Use AutoplaySource::NumberOfSources for invalid
   // source.
   AutoplaySource m_source;
   // The media element this UMA helper is attached to. |m_element| owns |this|.
   Member<HTMLMediaElement> m_element;
 
   // The observer is used to observe whether a muted video autoplaying by play()
   // method become visible at some point.
   // The UMA is pending for recording as long as this observer is non-null.
@@ skipping 17 matching lines @@
   // The observer is used to observer an autoplaying muted video changing it's
   // visibility, which is used for offscreen duration UMA.  The UMA is pending
   // for recording as long as this observer is non-null.
   Member<ElementVisibilityObserver>
       m_mutedVideoOffscreenDurationVisibilityObserver;
 };
 
 }  // namespace blink
 
 #endif  // AutoplayUmaHelper_h