When autoplaying muted video, record when unmute happen and the result.

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:
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  *    notice, this list of conditions and the following disclaimer.
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@@ skipping 2272 matching lines @@
 
 bool HTMLMediaElement::muted() const
 {
     return m_muted;
 }
 
 void HTMLMediaElement::setMuted(bool muted)
 {
     MEDIA_LOG << "setMuted(" << (void*)this << ", " << boolString(muted) << ")";
 
+    if (m_muted == muted)
+        return;
+
+    bool wasAutoplayingMuted = !paused() && m_muted && isLockedPendingUserGesture();
+
     if (UserGestureIndicator::processingUserGesture())

[whywhat, 2016/06/29 19:44:18]

nit: you could avoid moving that if calculating wasAutoplayingMuted above it.
Not sure though if it can happen that muted is changed with user gesture to the
same value and whether we should unlock the element in that case :) So perhaps
this move is okay.

[mlamouri (slow - plz ping), 2016/06/29 19:47:59]

ACK :)

         unlockUserGesture();
 
-    if (m_muted == muted)
-        return;
-
     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);
 
-    // Pause the element when unmuting if it's still locked.
-    if (!muted && isGestureNeededForPlayback())
-        pause();
+    // 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);
+        }
+    }
 }
 
 void HTMLMediaElement::updateVolume()
 {
     if (webMediaPlayer())
         webMediaPlayer()->setVolume(effectiveMediaVolume());
 
     if (mediaControls())
         mediaControls()->updateVolume();
 }
@@ skipping 1567 matching lines @@
 
     if (isHTMLVideoElement()) {
         videoHistogram.count(source);
         if (muted())
             mutedVideoHistogram.count(source);
     } else {
         audioHistogram.count(source);
     }
 }
 
+void HTMLMediaElement::recordAutoplayUnmuteStatus(AutoplayUnmuteActionStatus status)
+{
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, autoplayUnmuteHistogram, ("Media.Video.Autoplay.Muted.UnmuteAction", AutoplayUnmuteActionMax));
+
+    autoplayUnmuteHistogram.count(status);
+}
+
 void HTMLMediaElement::onVisibilityChangedForAutoplay(bool isVisible)
 {
     if (!isVisible)
         return;
 
     if (shouldAutoplay()) {
         m_paused = false;
         invalidateCachedTime();
         scheduleEvent(EventTypeNames::play);
         scheduleNotifyPlaying();
@@ skipping 112 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect() const
 {
     IntRect result;
     if (LayoutObject* object = m_element->layoutObject())
         result = object->absoluteBoundingBoxRect();
     return result;
 }
 
 } // namespace blink