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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 275 matching lines @@
 // These values are used for histograms. Do not reorder.
 enum AutoplaySource {
     // Autoplay comes from HTMLMediaElement `autoplay` attribute.
     AutoplaySourceAttribute = 0,
     // Autoplay comes from `play()` method.
     AutoplaySourceMethod = 1,
     // This enum value must be last.
     NumberOfAutoplaySources = 2,
 };
 
+// These values are used for histograms. Do not reorder.
+enum AutoplayUnmuteActionStatus {
+    AutoplayUnmuteActionFailure = 0,
+    AutoplayUnmuteActionSuccess = 1,
+    AutoplayUnmuteActionMax = 2,
+};
+
 } // anonymous namespace
 
 class HTMLMediaElement::AutoplayHelperClientImpl :
     public AutoplayExperimentHelper::Client {
 
 public:
     static AutoplayHelperClientImpl* create(HTMLMediaElement* element)
     {
         return new AutoplayHelperClientImpl(element);
     }
@@ skipping 1979 matching lines @@
 
 bool HTMLMediaElement::muted() const
 {
     return m_muted;
 }
 
 void HTMLMediaElement::setMuted(bool muted)
 {
     MEDIA_LOG << "setMuted(" << (void*)this << ", " << boolString(muted) << ")";
 
-    if (UserGestureIndicator::processingUserGesture())
-        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);
 
+    bool wasLocked = isGestureNeededForPlayback();

[whywhat, 2016/06/28 10:20:59]

nit: I think you either want:

bool wasLocked = m_lockedPendingUserGesture;

or

bool wasGestureNeededForPlayback = isGestureNeededForPlayback();

+    if (UserGestureIndicator::processingUserGesture())
+        unlockUserGesture();
+
+    // Record when unmuting a video that was autoplayed because it was muted.
+    if (wasLocked && !muted && isHTMLVideoElement() && RuntimeEnabledFeatures::autoplayMutedVideosEnabled())

[whywhat, 2016/06/28 10:20:59]

this condition seems to be very hard to read and maintain. Should've you checked
for data saver as well?

+        recordAutoplayUnmuteStatus(isGestureNeededForPlayback() ? AutoplayUnmuteStatus::Failure : AutoplayUnmuteStatus::Success);
+
     // Pause the element when unmuting if it's still locked.
     if (!muted && isGestureNeededForPlayback())

[whywhat, 2016/06/28 10:20:59]

// this implicitly relies on m_muted set to false beforehand, so I don't like it
much
// bool wasGestureNeededForPlayback = isGestureNeededForPlayback();

// this needs to be called at the top but at least the dependency is explicit
bool wasAutoplayingMuted = !paused() && m_muted && m_lockedPendingUserGesture;

// do other stuff, unlock the gesture if processing it
// ...

if (wasAutoplayingMuted) {
    if (isGestureNeededForPlayback())
        pause();
    recordAutoplayUnmutePausedState(paused());
}

wdyt?

         pause();
 }
 
 void HTMLMediaElement::updateVolume()
 {
     if (webMediaPlayer())
         webMediaPlayer()->setVolume(effectiveMediaVolume());
 
     if (mediaControls())
         mediaControls()->updateVolume();
@@ skipping 1558 matching lines @@
 
     if (isHTMLVideoElement()) {
         videoHistogram.count(source);
         if (muted())
             mutedVideoHistogram.count(source);
     } else {
         audioHistogram.count(source);
     }
 }
 
+void HTMLMediaElement::recordAutoplayUnmuteStatus(AutoplayUnmuteStatus status)
+{
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, autoplayUnmuteHistogram, ("Media.Video.Autoplay.Muted.UnmuteAction", AutoplayUnmuteActionMax));
+
+    autoplayUnmuteHistogram.count(status == AutoplayUnmuteStatus::Success ? AutoplayUnmuteActionSuccess : AutoplayUnmuteActionFailure);
+}
+
 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