Implement automatic text track selection for 'metadata' tracks

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 2903 matching lines @@
             RefPtrWillBeRawPtr<TextTrack> textTrack = currentlyEnabledTracks[i];
             if (textTrack != trackToEnable)
                 textTrack->setMode(TextTrack::disabledKeyword());
         }
     }
 
     if (trackToEnable)
         trackToEnable->setMode(TextTrack::showingKeyword());
 }
 
+void HTMLMediaElement::configureMetadataTextTrackGroup(const TrackGroup& group)
+{
+    ASSERT(group.tracks.size());
+
+    // https://html.spec.whatwg.org/multipage/embedded-content.html#honor-user-preferences-for-automatic-text-track-selection
+
+    // 4. If there are any text tracks in the media element's list of text
+    // tracks whose text track kind is metadata that correspond to track
+    // elements with a default attribute set whose text track mode is set to
+    // disabled, then set the text track mode of all such tracks to hidden
+    for (auto& textTrack : group.tracks) {
+        if (textTrack->mode() != TextTrack::disabledKeyword())
+            continue;
+        if (!textTrack->isDefault())
+            continue;
+        textTrack->setMode(TextTrack::hiddenKeyword());
+    }
+}
+
 void HTMLMediaElement::configureTextTracks()
 {
     TrackGroup captionAndSubtitleTracks(TrackGroup::CaptionsAndSubtitles);
     TrackGroup descriptionTracks(TrackGroup::Description);
     TrackGroup chapterTracks(TrackGroup::Chapter);
     TrackGroup metadataTracks(TrackGroup::Metadata);
     TrackGroup otherTracks(TrackGroup::Other);
 
     if (!m_textTracks)
         return;
@@ skipping 35 matching lines @@
         currentGroup->tracks.append(textTrack);
     }
 
     if (captionAndSubtitleTracks.tracks.size())
         configureTextTrackGroup(captionAndSubtitleTracks);
     if (descriptionTracks.tracks.size())
         configureTextTrackGroup(descriptionTracks);
     if (chapterTracks.tracks.size())
         configureTextTrackGroup(chapterTracks);
     if (metadataTracks.tracks.size())
-        configureTextTrackGroup(metadataTracks);
+        configureMetadataTextTrackGroup(metadataTracks);
     if (otherTracks.tracks.size())
         configureTextTrackGroup(otherTracks);
 
     textTracksChanged();
 }
 
 bool HTMLMediaElement::havePotentialSourceChild()
 {
     // Stash the current <source> node and next nodes so we can restore them after checking
     // to see there is another potential.
@@ skipping 1104 matching lines @@
 
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!visitor->isAlive(m_audioSourceNode) && audioSourceProvider())
         audioSourceProvider()->setClient(nullptr);
 }
 #endif
 
 }