Videojs自定义TextTrackDisplay不工作

<link href="https://vjs.zencdn.net/7.15.0/video-js.css" rel="stylesheet">
<script src="https://vjs.zencdn.net/7.15.0/video.js"></script>
<script src="https://unpkg.com/videojs-contrib-hls@5.15.0/dist/videojs-contrib-hls.js"></script>
<script src="https://unpkg.com/videojs-contrib-quality-levels@7.3.0/dist/videojs-contrib-quality-levels.js"></script>

<video id="my-video" class="video-js" controls preload="auto" width="640" height="360">
  <source src="my-video.mp4" type="video/mp4">
  <track kind="subtitles" src="subtitles.vtt" srclang="en" label="English" default>
  <track kind="subtitles" src="subtitles.zh.vtt" srclang="zh" label="中文">
</video>

<script>
videojs('my-video', {
  plugins: {
    qualityLevels: {
      name: 'qualityLevels',
      addQualityLevel: function() {}
    }
  }
}).ready(function() {
  var player = this;
  player.qualityLevels();
});
</script>

<script>
videojs.getComponent('TextTrackDisplay').prototype.handleClick = function() {
  // 自定义点击事件的处理逻辑
};

videojs.getComponent('TextTrackDisplay').prototype.createEl = function() {
  // 自定义TextTrackDisplay元素的创建逻辑
};
</script>