Support text track selection in video controls

third_party/WebKit/Source/core/html/track/TextTrack.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  * Copyright (C) 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 396 matching lines @@
 
     return m_trackIndex;
 }
 
 void TextTrack::invalidateTrackIndex()
 {
     m_trackIndex = invalidTrackIndex;
     m_renderedTrackIndex = invalidTrackIndex;
 }
 
-bool TextTrack::isRendered()
+bool TextTrack::isRendered() const
 {
     if (kind() != captionsKeyword() && kind() != subtitlesKeyword())
         return false;
 
     if (m_mode != showingKeyword())
         return false;
 
     return true;
 }
 
+bool TextTrack::canBeRendered() const
+{
+    // A track can be displayed when it's of kind captions or subtitles and hasn't failed to load.
+    if (kind() != captionsKeyword() && kind() != subtitlesKeyword())
+        return false;
+
+    if (getReadinessState() == FailedToLoad)
+        return false;
+
+    return true;
+}
+
 TextTrackCueList* TextTrack::ensureTextTrackCueList()
 {
     if (!m_cues)
         m_cues = TextTrackCueList::create();
 
     return m_cues.get();
 }
 
 int TextTrack::trackIndexRelativeToRenderedTracks()
 {
@@ skipping 35 matching lines @@
 {
     visitor->trace(m_cues);
     visitor->trace(m_activeCues);
     visitor->trace(m_regions);
     visitor->trace(m_trackList);
     TrackBase::trace(visitor);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink