Initial implementation of AudioTrack, AudioTrackList, VideoTrack, and VideoTrackList.

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 36 matching lines @@
 #include "core/html/HTMLMediaSource.h"
 #include "core/html/HTMLSourceElement.h"
 #include "core/html/HTMLTrackElement.h"
 #include "core/html/MediaController.h"
 #include "core/html/MediaError.h"
 #include "core/html/MediaFragmentURIParser.h"
 #include "core/html/MediaKeyError.h"
 #include "core/html/MediaKeyEvent.h"
 #include "core/html/TimeRanges.h"
 #include "core/html/shadow/MediaControls.h"
+#include "core/html/track/AudioTrack.h"
+#include "core/html/track/AudioTrackList.h"
 #include "core/html/track/InbandTextTrack.h"
 #include "core/html/track/TextTrackCueList.h"
 #include "core/html/track/TextTrackList.h"
+#include "core/html/track/VideoTrack.h"
+#include "core/html/track/VideoTrackList.h"
 #include "core/loader/FrameLoader.h"
 #include "core/rendering/RenderLayerCompositor.h"
 #include "core/rendering/RenderVideo.h"
 #include "core/rendering/RenderView.h"
 // FIXME: Remove dependency on modules/encryptedmedia (http://crbug.com/242754).
 #include "modules/encryptedmedia/MediaKeyNeededEvent.h"
 #include "modules/encryptedmedia/MediaKeys.h"
 #include "platform/ContentType.h"
 #include "platform/Language.h"
 #include "platform/Logging.h"
@@ skipping 225 matching lines @@
     , m_sentStalledEvent(false)
     , m_sentEndEvent(false)
     , m_pausedInternal(false)
     , m_closedCaptionsVisible(false)
     , m_completelyLoaded(false)
     , m_havePreparedToPlay(false)
     , m_tracksAreReady(true)
     , m_haveVisibleTextTrack(false)
     , m_processingPreferenceChange(false)
     , m_lastTextTrackUpdateTime(-1)
+    , m_audioTracks(nullptr)
+    , m_videoTracks(nullptr)
     , m_textTracks(nullptr)
     , m_ignoreTrackDisplayUpdate(0)
 #if ENABLE(WEB_AUDIO)
     , m_audioSourceNode(0)
 #endif
     , m_emeMode(EmeModeNotSelected)
 {
     ASSERT(RuntimeEnabledFeatures::mediaEnabled());
 
     WTF_LOG(Media, "HTMLMediaElement::HTMLMediaElement");
@@ skipping 13 matching lines @@
     addElementToDocumentMap(this, &document);
 }
 
 HTMLMediaElement::~HTMLMediaElement()
 {
     WTF_LOG(Media, "HTMLMediaElement::~HTMLMediaElement");
 
     m_asyncEventQueue->close();
 
     setShouldDelayLoadEvent(false);
+    if (m_audioTracks)
+        m_audioTracks->clearOwner();
+    if (m_videoTracks)
+        m_videoTracks->clearOwner();
     if (m_textTracks)
-        m_textTracks->clearOwner();
-    if (m_textTracks) {
-        for (unsigned i = 0; i < m_textTracks->length(); ++i)
-            m_textTracks->item(i)->clearClient();
-    }
+        m_textTracks->clearOwnerAndClients();
 
     if (m_mediaController) {
         m_mediaController->removeMediaElement(this);
         m_mediaController = nullptr;
     }
 
     closeMediaSource();
 
     setMediaKeysInternal(0);
 
@@ skipping 302 matching lines @@
     // a task to fire a simple event named abort at the media element.
     if (m_networkState == NETWORK_LOADING || m_networkState == NETWORK_IDLE)
         scheduleEvent(EventTypeNames::abort);
 
     closeMediaSource();
 
     createMediaPlayer();
 
     // 4 - If the media element's networkState is not set to NETWORK_EMPTY, then run these substeps
     if (m_networkState != NETWORK_EMPTY) {
+        // 4.1 - Queue a task to fire a simple event named emptied at the media element.
+        scheduleEvent(EventTypeNames::emptied);
+
+        // 4.2 - If a fetching process is in progress for the media element, the user agent should stop it.
         m_networkState = NETWORK_EMPTY;
+
+        // 4.3 - Forget the media element's media-resource-specific tracks.
+        forgetResourceSpecificTracks();
+
+        // 4.4 - If readyState is not set to HAVE_NOTHING, then set it to that state.
         m_readyState = HAVE_NOTHING;
         m_readyStateMaximum = HAVE_NOTHING;
+
+        // 4.5 - If the paused attribute is false, then set it to true.
+        m_paused = true;
+
+        // 4.6 - If seeking is true, set it to false.
+        m_seeking = false;
+
+        // 4.7 - Set the current playback position to 0.
+        //       Set the official playback position to 0.
+        //       If this changed the official playback position, then queue a task to fire a simple event named timeupdate at the media element.
+
+        // 4.8 - Set the initial playback position to 0.
+        // FIXME: Make this less subtle. The position only becomes 0 because of the createMediaPlayer() call
+        // above.
         refreshCachedTime();
-        m_paused = true;
-        m_seeking = false;
         invalidateCachedTime();
-        scheduleEvent(EventTypeNames::emptied);
+
+        // 4.9 - Set the timeline offset to Not-a-Number (NaN).
+        // 4.10 - Update the duration attribute to Not-a-Number (NaN).
+
         updateMediaController();
         if (RuntimeEnabledFeatures::videoTrackEnabled())
             updateActiveTextTrackCues(0);
     }
 
     // 5 - Set the playbackRate attribute to the value of the defaultPlaybackRate attribute.
     setPlaybackRate(defaultPlaybackRate());
 
     // 6 - Set the error attribute to null and the autoplaying flag to true.
     m_error = nullptr;
     m_autoplaying = true;
 
     // 7 - Invoke the media element's resource selection algorithm.
 
     // 8 - Note: Playback of any previously playing media resource for this element stops.
 
     // The resource selection algorithm
     // 1 - Set the networkState to NETWORK_NO_SOURCE
     m_networkState = NETWORK_NO_SOURCE;
 
     // 2 - Asynchronously await a stable state.
 
     m_playedTimeRanges = TimeRanges::create();
+
+    // FIXME: Investigate whether these can be moved into m_networkState != NETWORK_EMPTY block above
+    // so they are closer to the relevant spec steps.
     m_lastSeekTime = 0;
     m_duration = numeric_limits<double>::quiet_NaN();
 
     // The spec doesn't say to block the load event until we actually run the asynchronous section
     // algorithm, but do it now because we won't start that until after the timer fires and the
     // event may have already fired by then.
     setShouldDelayLoadEvent(true);
 
     configureMediaControls();
 }
@@ skipping 650 matching lines @@
 
     // 4.8.10.5
     // 6 - Reaching this step indicates that the media resource failed to load or that the given
     // URL could not be resolved. In one atomic operation, run the following steps:
 
     // 6.1 - Set the error attribute to a new MediaError object whose code attribute is set to
     // MEDIA_ERR_SRC_NOT_SUPPORTED.
     m_error = MediaError::create(MediaError::MEDIA_ERR_SRC_NOT_SUPPORTED);
 
     // 6.2 - Forget the media element's media-resource-specific text tracks.
+    forgetResourceSpecificTracks();
 
     // 6.3 - Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
     m_networkState = NETWORK_NO_SOURCE;
 
     // 7 - Queue a task to fire a simple event named error at the media element.
     scheduleEvent(EventTypeNames::error);
 
     closeMediaSource();
 
     // 8 - Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
@@ skipping 53 matching lines @@
     setNetworkState(m_player->networkState());
 }
 
 void HTMLMediaElement::mediaLoadingFailed(MediaPlayer::NetworkState error)
 {
     stopPeriodicTimers();
 
     // If we failed while trying to load a <source> element, the movie was never parsed, and there are more
     // <source> children, schedule the next one
     if (m_readyState < HAVE_METADATA && m_loadState == LoadingFromSourceElement) {
-
+        // resource selection algorithm
+        // Step 9.Otherwise.9 - Failed with elements: Queue a task, using the DOM manipulation task source, to fire a simple event named error at the candidate element.
         if (m_currentSourceNode)
             m_currentSourceNode->scheduleErrorEvent();
         else
             WTF_LOG(Media, "HTMLMediaElement::setNetworkState - error event not sent, <source> was removed");
 
+        // 9.Otherwise.10 - Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
+
+        // 9.Otherwise.11 Forget the media element's media-resource-specific tracks.
+        forgetResourceSpecificTracks();
+
         if (havePotentialSourceChild()) {
             WTF_LOG(Media, "HTMLMediaElement::setNetworkState - scheduling next <source>");
             scheduleNextSourceChild();
         } else {
             WTF_LOG(Media, "HTMLMediaElement::setNetworkState - no more <source> elements, waiting");
             waitForSourceChange();
         }
 
         return;
     }
@@ skipping 111 matching lines @@
             finishSeek();
     } else {
         if (wasPotentiallyPlaying && m_readyState < HAVE_FUTURE_DATA) {
             // 4.8.10.8
             scheduleTimeupdateEvent(false);
             scheduleEvent(EventTypeNames::waiting);
         }
     }
 
     if (m_readyState >= HAVE_METADATA && oldState < HAVE_METADATA) {
+        createPlaceholderTracksIfNecessary();
+
         prepareMediaFragmentURI();
+
+        selectInitialTracksIfNecessary();
+
         scheduleEvent(EventTypeNames::durationchange);
         if (isVideo())
             scheduleEvent(EventTypeNames::resize);
         scheduleEvent(EventTypeNames::loadedmetadata);
         if (hasMediaControls())
             mediaControls()->reset();
         if (renderer())
             renderer()->updateFromElement();
     }
 
@@ skipping 857 matching lines @@
         m_lastTimeUpdateEventWallTime = now;
         m_lastTimeUpdateEventMovieTime = movieTime;
     }
 }
 
 bool HTMLMediaElement::canPlay() const
 {
     return paused() || ended() || m_readyState < HAVE_METADATA;
 }
 
-void HTMLMediaElement::mediaPlayerDidAddTrack(WebInbandTextTrack* webTrack)
+AudioTrackList* HTMLMediaElement::audioTracks()
+{
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+
+    if (!m_audioTracks)
+        m_audioTracks = AudioTrackList::create(this);
+
+    return m_audioTracks.get();
+}
+
+void HTMLMediaElement::didEnabledAudioTrackChange(const AtomicString& audioTrackID, bool enabled)
+{
+    WTF_LOG(Media, "HTMLMediaElement::didEnabledAudioTrackChange('%s', %d)", audioTrackID.ascii().data(), enabled);
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+    ASSERT(!audioTrackID.isEmpty());
+
+    if (webMediaPlayer())
+        webMediaPlayer()->enabledAudioTrackChange(audioTrackID, enabled);
+}
+
+VideoTrackList* HTMLMediaElement::videoTracks()
+{
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+
+    if (!m_videoTracks)
+        m_videoTracks = VideoTrackList::create(this);
+
+    return m_videoTracks.get();
+}
+
+void HTMLMediaElement::didSelectedVideoTrackChange(const AtomicString& unselectedTrackID, const AtomicString& selectedTrackID)
+{
+    WTF_LOG(Media, "HTMLMediaElement::didSelectedVideoTrackChange('%s', '%s')", unselectedTrackID.ascii().data(), selectedTrackID.ascii().data());
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+    ASSERT(!unselectedTrackID.isEmpty() || !selectedTrackID.isEmpty());
+
+    if (webMediaPlayer())
+        webMediaPlayer()->selectedVideoTrackChange(unselectedTrackID, selectedTrackID);
+}
+
+void HTMLMediaElement::mediaPlayerDidAddVideoTrack(const AtomicString& id, const AtomicString& kind, const AtomicString& label, const AtomicString& language, bool selected)
+{
+    WTF_LOG(Media, "HTMLMediaElement::mediaPlayerDidAddVideoTrack('%s', '%s', '%s', '%s', %d)",
+        id.ascii().data(), kind.ascii().data(), label.ascii().data(), language.ascii().data(), selected);
+    ASSERT(!id.isEmpty());
+
+    RefPtr<VideoTrack> videoTrack = VideoTrack::create(videoTracks(), id, kind, label, language);
+    videoTracks()->add(videoTrack.get());
+
+    if (selected)
+        videoTrack->setSelected(true);
+}
+
+void HTMLMediaElement::mediaPlayerDidRemoveVideoTrack(const AtomicString& id)
+{
+    WTF_LOG(Media, "HTMLMediaElement::mediaPlayerDidRevmoeVideoTrack('%s')", id.ascii().data());
+    ASSERT(!id.isEmpty());
+
+    if (!RuntimeEnabledFeatures::audioVideoTracksEnabled())
+        return;
+
+    videoTracks()->remove(id);
+}
+
+void HTMLMediaElement::mediaPlayerDidAddAudioTrack(const AtomicString& id, const AtomicString& kind, const AtomicString& label, const AtomicString& language, bool enabled)
+{
+    WTF_LOG(Media, "HTMLMediaElement::mediaPlayerDidAddAudioTrack('%s', '%s', '%s', '%s', %d)",
+        id.ascii().data(), kind.ascii().data(), label.ascii().data(), language.ascii().data(), enabled);
+    ASSERT(!id.isEmpty());
+
+    if (!RuntimeEnabledFeatures::audioVideoTracksEnabled())
+        return;
+
+    AtomicString kindString;
+    RefPtr<AudioTrack> audioTrack = AudioTrack::create(audioTracks(), id, kind, label, language);
+    audioTracks()->add(audioTrack.get());
+
+    if (enabled)
+        audioTrack->setEnabled(true);
+}
+
+void HTMLMediaElement::mediaPlayerDidRemoveAudioTrack(const AtomicString& id)
+{
+    WTF_LOG(Media, "HTMLMediaElement::mediaPlayerDidRevmoeAudioTrack('%s')", id.ascii().data());
+    ASSERT(!id.isEmpty());
+
+    if (!RuntimeEnabledFeatures::audioVideoTracksEnabled())
+        return;
+
+    audioTracks()->remove(id);
+}
+
+void HTMLMediaElement::mediaPlayerDidAddTextTrack(WebInbandTextTrack* webTrack)
 {
     if (!RuntimeEnabledFeatures::videoTrackEnabled())
         return;
 
     // 4.8.10.12.2 Sourcing in-band text tracks
     // 1. Associate the relevant data with a new text track and its corresponding new TextTrack object.
     RefPtr<InbandTextTrack> textTrack = InbandTextTrack::create(document(), this, webTrack);
 
     // 2. Set the new text track's kind, label, and language based on the semantics of the relevant data,
     // as defined by the relevant specification. If there is no label in that data, then the label must
@@ skipping 11 matching lines @@
 
     // 7. Set the new text track's mode to the mode consistent with the user's preferences and the requirements of
     // the relevant specification for the data.
     //  - This will happen in configureTextTracks()
     scheduleDelayedAction(LoadTextTrackResource);
 
     // 8. Add the new text track to the media element's list of text tracks.
     // 9. Fire an event with the name addtrack, that does not bubble and is not cancelable, and that uses the TrackEvent
     // interface, with the track attribute initialized to the text track's TextTrack object, at the media element's
     // textTracks attribute's TextTrackList object.
-    addTrack(textTrack.get());
+    addTextTrack(textTrack.get());
 }
 
-void HTMLMediaElement::mediaPlayerDidRemoveTrack(WebInbandTextTrack* webTrack)
+void HTMLMediaElement::mediaPlayerDidRemoveTextTrack(WebInbandTextTrack* webTrack)
 {
     if (!RuntimeEnabledFeatures::videoTrackEnabled())
         return;
 
     if (!m_textTracks)
         return;
 
     // This cast is safe because we created the InbandTextTrack with the WebInbandTextTrack
     // passed to mediaPlayerDidAddTrack.
     RefPtr<InbandTextTrack> textTrack = static_cast<InbandTextTrack*>(webTrack->client());
     if (!textTrack)
         return;
 
-    removeTrack(textTrack.get());
+    removeTextTrack(textTrack.get(), true);
 }
 
 void HTMLMediaElement::closeCaptionTracksChanged()
 {
     if (hasMediaControls())
         mediaControls()->closedCaptionTracksChanged();
 }
 
-void HTMLMediaElement::addTrack(TextTrack* track)
+void HTMLMediaElement::addTextTrack(TextTrack* track)
 {
     textTracks()->append(track);
 
     closeCaptionTracksChanged();
 }
 
-void HTMLMediaElement::removeTrack(TextTrack* track)
+void HTMLMediaElement::removeTextTrack(TextTrack* track, bool fireRemoveTrackEvent)
 {
     TrackDisplayUpdateScope scope(this);
     TextTrackCueList* cues = track->cues();
     if (cues)
         textTrackRemoveCues(track, cues);
-    m_textTracks->remove(track);
+    m_textTracks->remove(track, fireRemoveTrackEvent);
 
     closeCaptionTracksChanged();
 }
 
-void HTMLMediaElement::removeAllInbandTracks()
+void HTMLMediaElement::forgetResourceSpecificTracks()
 {
-    if (!m_textTracks)
-        return;
+    // Implements the "forget the media element's media-resource-specific tracks" algorithm.
+    // The order is explicitly specified as text, then audio, and finally video. Also
+    // 'removetrack' events should not be fired.
+    if (m_textTracks) {
+        TrackDisplayUpdateScope scope(this);
+        for (int i = m_textTracks->length() - 1; i >= 0; --i) {
+            TextTrack* track = m_textTracks->item(i);
 
-    TrackDisplayUpdateScope scope(this);
-    for (int i = m_textTracks->length() - 1; i >= 0; --i) {
-        TextTrack* track = m_textTracks->item(i);
+            if (track->trackType() == TextTrack::InBand)
+                removeTextTrack(track, false);
+        }
+    }
 
-        if (track->trackType() == TextTrack::InBand)
-            removeTrack(track);
-    }
+    if (m_audioTracks)
+        m_audioTracks->removeAll();
+
+    if (m_videoTracks)
+        m_videoTracks->removeAll();
 }
 
 PassRefPtr<TextTrack> HTMLMediaElement::addTextTrack(const AtomicString& kind, const AtomicString& label, const AtomicString& language, ExceptionState& exceptionState)
 {
     ASSERT(RuntimeEnabledFeatures::videoTrackEnabled());
 
     // 4.8.10.12.4 Text track API
     // The addTextTrack(kind, label, language) method of media elements, when invoked, must run the following steps:
 
     // 1. If kind is not one of the following strings, then throw a SyntaxError exception and abort these steps
     if (!TextTrack::isValidKindKeyword(kind)) {
         exceptionState.throwDOMException(SyntaxError, "The 'kind' provided ('" + kind + "') is invalid.");
         return nullptr;
     }
 
     // 2. If the label argument was omitted, let label be the empty string.
     // 3. If the language argument was omitted, let language be the empty string.
     // 4. Create a new TextTrack object.
 
     // 5. Create a new text track corresponding to the new object, and set its text track kind to kind, its text
     // track label to label, its text track language to language...
     RefPtr<TextTrack> textTrack = TextTrack::create(document(), this, kind, label, language);
 
     // Note, due to side effects when changing track parameters, we have to
     // first append the track to the text track list.
 
     // 6. Add the new text track to the media element's list of text tracks.
-    addTrack(textTrack.get());
+    addTextTrack(textTrack.get());
 
     // ... its text track readiness state to the text track loaded state ...
     textTrack->setReadinessState(TextTrack::Loaded);
 
     // ... its text track mode to the text track hidden mode, and its text track list of cues to an empty list ...
     textTrack->setMode(TextTrack::hiddenKeyword());
 
     return textTrack.release();
 }
 
@@ skipping 15 matching lines @@
         return;
 
     // 4.8.10.12.3 Sourcing out-of-band text tracks
     // When a track element's parent element changes and the new parent is a media element,
     // then the user agent must add the track element's corresponding text track to the
     // media element's list of text tracks ... [continues in TextTrackList::append]
     RefPtr<TextTrack> textTrack = trackElement->track();
     if (!textTrack)
         return;
 
-    addTrack(textTrack.get());
+    addTextTrack(textTrack.get());
 
     // Do not schedule the track loading until parsing finishes so we don't start before all tracks
     // in the markup have been added.
     if (isFinishedParsingChildren())
         scheduleDelayedAction(LoadTextTrackResource);
 
     if (hasMediaControls())
         mediaControls()->closedCaptionTracksChanged();
 }
 
@@ skipping 17 matching lines @@
 
     textTrack->setHasBeenConfigured(false);
 
     if (!m_textTracks)
         return;
 
     // 4.8.10.12.3 Sourcing out-of-band text tracks
     // When a track element's parent element changes and the old parent was a media element,
     // then the user agent must remove the track element's corresponding text track from the
     // media element's list of text tracks.
-    removeTrack(textTrack.get());
+    removeTextTrack(textTrack.get(), true);
 
     size_t index = m_textTracksWhenResourceSelectionBegan.find(textTrack.get());
     if (index != kNotFound)
         m_textTracksWhenResourceSelectionBegan.remove(index);
 }
 
 static int textTrackLanguageSelectionScore(const TextTrack& track)
 {
     if (track.language().isEmpty())
         return 0;
@@ skipping 732 matching lines @@
     m_player.clear();
 
 #if ENABLE(WEB_AUDIO)
     if (m_audioSourceNode)
         m_audioSourceNode->unlock();
 #endif
 }
 
 void HTMLMediaElement::clearMediaPlayer(int flags)
 {
-    removeAllInbandTracks();
+    forgetResourceSpecificTracks();
 
     closeMediaSource();
 
     setMediaKeysInternal(0);
 
     clearMediaPlayerAndAudioSourceProviderClient();
 
     stopPeriodicTimers();
     m_loadTimer.stop();
 
@@ skipping 446 matching lines @@
         m_fragmentStartTime = MediaPlayer::invalidTime();
 
     double end = fragmentParser.endTime();
     if (end != MediaFragmentURIParser::invalidTimeValue() && end > 0 && end > m_fragmentStartTime) {
         m_fragmentEndTime = end;
         if (m_fragmentEndTime > dur)
             m_fragmentEndTime = dur;
     } else
         m_fragmentEndTime = MediaPlayer::invalidTime();
 
+    // FIXME: Add support for selecting tracks by ID with the Media Fragments track dimension.
+
     if (m_fragmentStartTime != MediaPlayer::invalidTime() && m_readyState < HAVE_FUTURE_DATA)
         prepareToPlay();
 }
 
 void HTMLMediaElement::applyMediaFragmentURI()
 {
     if (m_fragmentStartTime != MediaPlayer::invalidTime()) {
         m_sentEndEvent = false;
         seek(m_fragmentStartTime, IGNORE_EXCEPTION);
     }
@@ skipping 42 matching lines @@
 void HTMLMediaElement::mediaPlayerMediaSourceOpened(blink::WebMediaSource* webMediaSource)
 {
     m_mediaSource->setWebMediaSourceAndOpen(adoptPtr(webMediaSource));
 }
 
 bool HTMLMediaElement::isInteractiveContent() const
 {
     return fastHasAttribute(controlsAttr);
 }
 
+void HTMLMediaElement::createPlaceholderTracksIfNecessary()
+{
+    if (!RuntimeEnabledFeatures::audioVideoTracksEnabled())
+        return;
+
+    // Create a placeholder audio track if |m_player| says it has audio but it didn't explicitly announce the tracks.
+    if (m_player->hasAudio() && !audioTracks()->length())
+        mediaPlayerDidAddAudioTrack("audio", AudioTrack::mainKeyword(), "Audio Track", "", true);
+
+    // Create a placeholder video track if |m_player| says it has video but it didn't explicitly announce the tracks.
+    if (m_player->hasVideo() && !videoTracks()->length())
+        mediaPlayerDidAddVideoTrack("video", VideoTrack::mainKeyword(), "Video Track", "", true);
 }
+
+void HTMLMediaElement::selectInitialTracksIfNecessary()
+{
+    if (!RuntimeEnabledFeatures::audioVideoTracksEnabled())
+        return;
+
+    // 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);
+}
+
+}