Implement autoplay gesture override experiment.

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 229 matching lines @@
     // when used with parameters, e.g. "application/octet-stream;codecs=theora", is a type that the user agent knows
     // it cannot render.
     if (contentMIMEType != "application/octet-stream" || contentTypeCodecs.isEmpty()) {
         WebMimeRegistry::SupportsType supported = Platform::current()->mimeRegistry()->supportsMediaMIMEType(contentMIMEType, contentTypeCodecs, keySystem.lower());
         return supported > WebMimeRegistry::IsNotSupported;
     }
 
     return false;
 }
 
-// These values are used for a histogram. Do not reorder.
-enum AutoplayMetrics {
-    // Media element with autoplay seen.
-    AutoplayMediaFound = 0,
-    // Autoplay enabled and user stopped media play at any point.
-    AutoplayStopped = 1,
-    // Autoplay enabled but user bailed out on media play early.
-    AutoplayBailout = 2,
-    // Autoplay disabled but user manually started media.
-    AutoplayManualStart = 3,
-    // Autoplay was (re)enabled through a user-gesture triggered load()
-    AutoplayEnabledThroughLoad = 4,
-    // Autoplay disabled by sandbox flags.
-    AutoplayDisabledBySandbox = 5,
-    // This enum value must be last.
-    NumberOfAutoplayMetrics,
-};
-
-static void recordAutoplayMetric(AutoplayMetrics metric)
+void HTMLMediaElement::recordAutoplayMetric(AutoplayMetrics metric)
 {
     Platform::current()->histogramEnumeration("Blink.MediaElement.Autoplay", metric, NumberOfAutoplayMetrics);
 }
 
 WebMimeRegistry::SupportsType HTMLMediaElement::supportsType(const ContentType& contentType, const String& keySystem)
 {
     DEFINE_STATIC_LOCAL(const String, codecs, ("codecs"));
 
     if (!RuntimeEnabledFeatures::mediaEnabled())
         return WebMimeRegistry::IsNotSupported;
@@ skipping 69 matching lines @@
     , m_sentEndEvent(false)
     , m_closedCaptionsVisible(false)
     , m_completelyLoaded(false)
     , m_havePreparedToPlay(false)
     , m_tracksAreReady(true)
     , m_haveVisibleTextTrack(false)
     , m_processingPreferenceChange(false)
     , m_remoteRoutesAvailable(false)
     , m_playingRemotely(false)
     , m_isFinalizing(false)
-    , m_initialPlayWithoutUserGestures(false)
+    , m_initialPlayWithoutUserGesture(false)
     , m_autoplayMediaCounted(false)
     , m_inOverlayFullscreenVideo(false)
     , m_audioTracks(AudioTrackList::create(*this))
     , m_videoTracks(VideoTrackList::create(*this))
     , m_textTracks(nullptr)
 #if ENABLE(WEB_AUDIO)
     , m_audioSourceNode(nullptr)
 #endif
+    , m_autoplayHelper(*this)
 {
 #if ENABLE(OILPAN)
     ThreadState::current()->registerPreFinalizer(this);
 #endif
     ASSERT(RuntimeEnabledFeatures::mediaEnabled());
 
     WTF_LOG(Media, "HTMLMediaElement::HTMLMediaElement(%p)", this);
 
     if (document.settings() && document.settings()->mediaPlaybackRequiresUserGesture())
         m_userGestureRequiredForPlay = true;
 
     setHasCustomStyleCallbacks();
     addElementToDocumentMap(this, &document);
 }
 
 HTMLMediaElement::~HTMLMediaElement()
 {
     WTF_LOG(Media, "HTMLMediaElement::~HTMLMediaElement(%p)", this);
+
 #if !ENABLE(OILPAN)
     // HTMLMediaElement and m_asyncEventQueue always become unreachable
     // together. So HTMLMediaElement and m_asyncEventQueue are destructed in
     // the same GC. We don't need to close it explicitly in Oilpan.
     m_asyncEventQueue->close();
 
     setShouldDelayLoadEvent(false);
 
     if (m_textTracks)
         m_textTracks->clearOwner();
@@ skipping 289 matching lines @@
     case WebMimeRegistry::IsSupported:
         canPlay = "probably";
         break;
     }
 
     WTF_LOG(Media, "HTMLMediaElement::canPlayType(%p, %s, %s) -> %s", this, mimeType.utf8().data(), keySystem.utf8().data(), canPlay.utf8().data());
 
     return canPlay;
 }
 
+void HTMLMediaElement::recordMetricsIfPausing()
+{
+    // If not playing, then nothing to record.
+    // TODO(liberato): test metrics.  this was m_paused.
+    if (m_paused)
+        return;
+
+    const bool bailout = isBailout();
+
+    // Record that play was paused.  We don't care if it was autoplay,
+    // play(), or the user manually started it.
+    recordAutoplayMetric(AnyPlaybackPaused);
+    if (bailout)
+        recordAutoplayMetric(AnyPlaybackBailout);
+
+    // If this was a gestureless play, then record that separately.
+    // These cover attr and play() gestureless starts.
+    if (m_initialPlayWithoutUserGesture) {
+        m_initialPlayWithoutUserGesture = false;
+
+        recordAutoplayMetric(AutoplayPaused);
+
+        if (bailout)
+            recordAutoplayMetric(AutoplayBailout);
+    }
+}
+
 void HTMLMediaElement::load()
 {
     WTF_LOG(Media, "HTMLMediaElement::load(%p)", this);
 
-    if (m_initialPlayWithoutUserGestures && m_playing)
-        gesturelessInitialPlayHalted();
+    recordMetricsIfPausing();
 
     if (UserGestureIndicator::processingUserGesture() && m_userGestureRequiredForPlay) {
         recordAutoplayMetric(AutoplayEnabledThroughLoad);
         m_userGestureRequiredForPlay = false;
         // While usergesture-initiated load()s technically count as autoplayed,
         // they don't feel like such to the users and hence we don't want to
         // count them for the purposes of metrics.
         m_autoplayMediaCounted = true;
     }
 
@@ skipping 838 matching lines @@
             scheduleEvent(EventTypeNames::canplay);
             if (isPotentiallyPlaying)
                 scheduleEvent(EventTypeNames::playing);
         }
 
         if (m_autoplaying && m_paused && autoplay()) {
             autoplayMediaEncountered();
 
             if (document().isSandboxed(SandboxAutomaticFeatures)) {
                 recordAutoplayMetric(AutoplayDisabledBySandbox);
-            } else if (!m_userGestureRequiredForPlay) {
-                m_paused = false;
-                invalidateCachedTime();
-                scheduleEvent(EventTypeNames::play);
-                scheduleEvent(EventTypeNames::playing);
+            } else {
+                // If the autoplay experiment says that it's okay to play now,
+                // then don't require a user gesture.
+                m_autoplayHelper.becameReadyToPlay();
+
+                if (!m_userGestureRequiredForPlay) {
+                    m_paused = false;
+                    invalidateCachedTime();
+                    scheduleEvent(EventTypeNames::play);
+                    scheduleEvent(EventTypeNames::playing);
+                }
             }
         }
 
         scheduleEvent(EventTypeNames::canplaythrough);
 
         shouldUpdateDisplayState = true;
     }
 
     if (shouldUpdateDisplayState) {
         updateDisplayState();
@@ skipping 112 matching lines @@
 
     m_lastSeekTime = time;
     m_sentEndEvent = false;
 
     // 10 - Queue a task to fire a simple event named seeking at the element.
     scheduleEvent(EventTypeNames::seeking);
 
     // 11 - Set the current playback position to the given new playback position.
     webMediaPlayer()->seek(time);
 
-    m_initialPlayWithoutUserGestures = false;
+    m_initialPlayWithoutUserGesture = false;
 
     // 14-17 are handled, if necessary, when the engine signals a readystate change or otherwise
     // satisfies seek completion and signals a time change.
 }
 
 void HTMLMediaElement::finishSeek()
 {
     WTF_LOG(Media, "HTMLMediaElement::finishSeek(%p)", this);
 
     // 14 - Set the seeking IDL attribute to false.
@@ skipping 170 matching lines @@
     // The ended attribute must return true if the media element has ended
     // playback and the direction of playback is forwards, and false otherwise.
     return endedPlayback() && directionOfPlayback() == Forward;
 }
 
 bool HTMLMediaElement::autoplay() const
 {
     return fastHasAttribute(autoplayAttr);
 }
 
+bool HTMLMediaElement::shouldAutoplay() const
+{
+    return m_autoplaying && autoplay();

[philipj_slow, 2015/09/04 09:24:27]

Can you also add m_paused and the sandbox requirement to the definition, to
match the spec? It says "If the autoplaying flag is true, and the paused
attribute is true, and the media element has an autoplay attribute specified,
and the media element's node document's active sandboxing flag set does not have
the sandboxed automatic features browsing context flag set"

Then use this same helper also in HTMLMediaElement::setReadyState. I realize
that this creates some trouble for recording metrics, perhaps the reason for
disallowing autoplay can be an out variable, or this could be turned into
allowAutoplay(), kind of like allowFullscreen, which is internally two other
methods used by HTMLMediaElement::setReadyState with ASSERTS to guarantee that
the usage of these are the same in both places.

The important point, of course, is that we should use exactly the same
definition of "can we autoplay?" in all contexts.

[liberato (no reviews please), 2015/09/08 21:58:01]

done.  i just moved the metrics recording into shouldAutoplay() and sent in a
bool.  that keeps the logic in one place.

[philipj_slow, 2015/09/10 10:05:13]

Did you forget to upload some changes? I can't see this change between PS27 and
PS28.

[liberato (no reviews please), 2015/09/10 14:52:27]

this was applied to the branch with visibility checks inadvertently, too.  i've
moved it back here.

+}
+
 String HTMLMediaElement::preload() const
 {
     switch (preloadType()) {
     case WebMediaPlayer::PreloadNone:
         return "none";
     case WebMediaPlayer::PreloadMetaData:
         return "metadata";
     case WebMediaPlayer::PreloadAuto:
         return "auto";
     }
@@ skipping 39 matching lines @@
 
 WebMediaPlayer::Preload HTMLMediaElement::effectivePreloadType() const
 {
     return autoplay() ? WebMediaPlayer::PreloadAuto : preloadType();
 }
 
 void HTMLMediaElement::play()
 {
     WTF_LOG(Media, "HTMLMediaElement::play(%p)", this);
 
+    m_autoplayHelper.playMethodCalled();
+
     if (!UserGestureIndicator::processingUserGesture()) {
         autoplayMediaEncountered();
+
         if (m_userGestureRequiredForPlay) {
+            recordAutoplayMetric(PlayMethodFailed);
             String message = ExceptionMessages::failedToExecute("play", "HTMLMediaElement", "API can only be initiated by a user gesture.");
             document().executionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
             return;
         }
     } else if (m_userGestureRequiredForPlay) {
         if (m_autoplayMediaCounted)
             recordAutoplayMetric(AutoplayManualStart);
         m_userGestureRequiredForPlay = false;
     }
 
@@ skipping 33 matching lines @@
     updateMediaController();
 }
 
 void HTMLMediaElement::autoplayMediaEncountered()
 {
     if (!m_autoplayMediaCounted) {
         m_autoplayMediaCounted = true;
         recordAutoplayMetric(AutoplayMediaFound);
 
         if (!m_userGestureRequiredForPlay)
-            m_initialPlayWithoutUserGestures = true;
+            m_initialPlayWithoutUserGesture = true;
     }
 }
 
-void HTMLMediaElement::gesturelessInitialPlayHalted()
+bool HTMLMediaElement::isBailout() const
 {
-    ASSERT(m_initialPlayWithoutUserGestures);
-    m_initialPlayWithoutUserGestures = false;
-
-    recordAutoplayMetric(AutoplayStopped);
-
     // We count the user as having bailed-out on the video if they watched
     // less than one minute and less than 50% of it.
-    double playedTime = currentTime();
-    if (playedTime < 60) {
-        double progress = playedTime / duration();
-        if (progress < 0.5)
-            recordAutoplayMetric(AutoplayBailout);
-    }
+    const double playedTime = currentTime();
+    const double progress = playedTime / duration();
+    return (playedTime < 60) && (progress < 0.5);
 }
 
 void HTMLMediaElement::pause()
 {
     WTF_LOG(Media, "HTMLMediaElement::pause(%p)", this);
 
     if (m_networkState == NETWORK_EMPTY)
         scheduleDelayedAction(LoadMediaResource);
 
+    m_autoplayHelper.pauseMethodCalled();
+
     m_autoplaying = false;
 
     if (!m_paused) {
-        if (m_initialPlayWithoutUserGestures)
-            gesturelessInitialPlayHalted();
+        recordMetricsIfPausing();
 
         m_paused = true;
         scheduleTimeupdateEvent(false);
         scheduleEvent(EventTypeNames::pause);
     }
 
     updatePlayState();
 }
 
 void HTMLMediaElement::requestRemotePlayback()
@@ skipping 72 matching lines @@
 
 void HTMLMediaElement::setMuted(bool muted)
 {
     WTF_LOG(Media, "HTMLMediaElement::setMuted(%p, %s)", this, boolString(muted));
 
     if (m_muted == muted)
         return;
 
     m_muted = muted;
 
+    m_autoplayHelper.mutedChanged();
+
     updateVolume();
 
     scheduleEvent(EventTypeNames::volumechange);
 }
 
 void HTMLMediaElement::updateVolume()
 {
     if (webMediaPlayer())
         webMediaPlayer()->setVolume(effectiveMediaVolume());
 
@@ skipping 611 matching lines @@
             if (!m_mediaController && !m_paused) {
                 // changes paused to true and fires a simple event named pause at the media element.
                 m_paused = true;
                 scheduleEvent(EventTypeNames::pause);
             }
             // Queue a task to fire a simple event named ended at the media element.
             if (!m_sentEndEvent) {
                 m_sentEndEvent = true;
                 scheduleEvent(EventTypeNames::ended);
             }
+            recordMetricsIfPausing();
             // If the media element has a current media controller, then report the controller state
             // for the media element's current media controller.
             updateMediaController();
         }
     } else {
         m_sentEndEvent = false;
     }
 
     updatePlayState();
 }
@@ skipping 200 matching lines @@
             // The media engine should just stash the rate and muted values since it isn't already playing.
             webMediaPlayer()->setRate(effectivePlaybackRate());
             updateVolume();
             webMediaPlayer()->play();
         }
 
         if (mediaControls())
             mediaControls()->playbackStarted();
         startPlaybackProgressTimer();
         m_playing = true;
+        recordAutoplayMetric(AnyPlaybackStarted);
 
     } else { // Should not be playing right now
         if (isPlaying)
             webMediaPlayer()->pause();
         refreshCachedTime();
 
         m_playbackProgressTimer.stop();
         m_playing = false;
         double time = currentTime();
         if (time > m_lastSeekTime)
@@ skipping 99 matching lines @@
         mediaControls()->refreshCastButtonVisibilityWithoutUpdate();
 
     if (layoutObject())
         layoutObject()->setShouldDoFullPaintInvalidation();
 }
 
 void HTMLMediaElement::stop()
 {
     WTF_LOG(Media, "HTMLMediaElement::stop(%p)", this);
 
-    if (m_playing && m_initialPlayWithoutUserGestures)
-        gesturelessInitialPlayHalted();
+    recordMetricsIfPausing();
 
     // Close the async event queue so that no events are enqueued by userCancelledLoad.
     cancelPendingEventsAndCallbacks();
     m_asyncEventQueue->close();
 
     userCancelledLoad();
 
     // Stop the playback without generating events
     m_playing = false;
     m_paused = true;
@@ skipping 593 matching lines @@
 
     // Enable the first audio track if an audio track hasn't been enabled yet.
     if (audioTracks().length() > 0 && !audioTracks().hasEnabledTrack())
         audioTracks().anonymousIndexedGetter(0)->setEnabled(true);
 
     // Select the first video track if a video track hasn't been selected yet.
     if (videoTracks().length() > 0 && videoTracks().selectedIndex() == -1)
         videoTracks().anonymousIndexedGetter(0)->setSelected(true);
 }
 
+bool HTMLMediaElement::isUserGestureRequiredForPlay() const
+{
+    return m_userGestureRequiredForPlay;
+}
+
+void HTMLMediaElement::removeUserGestureRequirement()
+{
+    m_userGestureRequiredForPlay = false;
+}
+
+void HTMLMediaElement::setInitialPlayWithoutUserGestures(bool value)
+{
+    m_initialPlayWithoutUserGesture = value;
+}
+
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!Heap::isHeapObjectAlive(m_audioSourceNode))
         audioSourceProvider().setClient(nullptr);
 }
 
 void HTMLMediaElement::AudioSourceProviderImpl::wrap(WebAudioSourceProvider* provider)
 {
     MutexLocker locker(provideInputLock);
@@ skipping 49 matching lines @@
     visitor->trace(m_client);
 }
 
 DEFINE_TRACE(HTMLMediaElement::AudioSourceProviderImpl)
 {
     visitor->trace(m_client);
 }
 #endif
 
 }