constructor(wsInstance) {
    /**
     * @type {WebSlides}
     * @private
     */
    this.ws_ = wsInstance;

    this.videos = DOM.toArray(this.ws_.el.querySelectorAll('[data-youtube]'));

    if (this.videos.length) {
      this.inject();
    }
  }
Grid plugin that shows a grid on top of the WebSlides for easy prototyping.
@param {WebSlides} wsInstance The WebSlides instance