hideAllTracks() {
    if (this.node.textTracks) {
      // parse through TextTrackList (not an Array)
      for (let i = 0; i < this.node.textTracks.length; i++) {
        this.node.textTracks[i].mode = 'hidden';
      }
    }
  }
Set mode for all tracks to 'hidden' (causes player to load them).