getTextTracks() {
    if (this.manifest_) {
      if (this.isRemotePlayback()) {
        return [];
      } else {
        const currentTextStream = this.streamingEngine_ ?
          this.streamingEngine_.getCurrentTextStream() : null;
        const tracks = [];

        // Convert all selectable text streams to tracks.
        for (const text of this.manifest_.textStreams) {
          const track = shaka.util.StreamUtils.textStreamToTrack(text);
          track.active = text == currentTextStream;

          tracks.push(track);
        }

        return tracks;
      }
    } else if (this.video_ && this.video_.src && this.video_.textTracks) {
      const textTracks = this.getFilteredTextTracks_();
      const StreamUtils = shaka.util.StreamUtils;
      return textTracks.map((text) => StreamUtils.html5TextTrackToTrack(text));
    } else {
      return [];
    }
  }
Return a list of text tracks that can be switched to.

<p>
If the player has not loaded content, this will return an empty list.

@return {!Array<shaka.extern.TextTrack>}
@export