Cancel autoplay muted when visible if the video gets unmuted before being visible.

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

 /*
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 2267 matching lines @@
 }
 
 void HTMLMediaElement::setMuted(bool muted)
 {
     MEDIA_LOG << "setMuted(" << (void*)this << ", " << boolString(muted) << ")";
 
     if (m_muted == muted)
         return;
 
     bool wasAutoplayingMuted = !paused() && m_muted && isLockedPendingUserGesture();
+    bool wasPendingAutoplayMuted = m_autoplayVisibilityObserver && paused() && m_muted && isLockedPendingUserGesture();
 
     if (UserGestureIndicator::processingUserGesture())
         unlockUserGesture();
 
     m_muted = muted;
     m_autoplayHelper->mutedChanged();
 
     updateVolume();
 
     if (muted)
         Platform::current()->recordAction(UserMetricsAction("Media_Playback_Mute_On"));
     else
         Platform::current()->recordAction(UserMetricsAction("Media_Playback_Mute_Off"));
 
     scheduleEvent(EventTypeNames::volumechange);
 
     // If an element autoplayed while muted, it needs to be unlocked to unmute,
     // otherwise, it will be paused.
     if (wasAutoplayingMuted) {
         if (isGestureNeededForPlayback()) {
             pause();
             recordAutoplayUnmuteStatus(AutoplayUnmuteActionFailure);
         } else {
             recordAutoplayUnmuteStatus(AutoplayUnmuteActionSuccess);
         }
     }
+
+    // If an element was a candidate for autoplay muted but not visible, it will
+    // have a visibility observer ready to start its playback.
+    if (wasPendingAutoplayMuted) {
+        m_autoplayVisibilityObserver->stop();
+        m_autoplayVisibilityObserver = nullptr;
+    }
 }
 
 void HTMLMediaElement::updateVolume()
 {
     if (webMediaPlayer())
         webMediaPlayer()->setVolume(effectiveMediaVolume());
 
     if (mediaControls())
         mediaControls()->updateVolume();
 }
@@ skipping 1709 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect() const
 {
     IntRect result;
     if (LayoutObject* object = m_element->layoutObject())
         result = object->absoluteBoundingBoxRect();
     return result;
 }
 
 } // namespace blink