I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

if (!this.pagesCount) {
      return { views: [] };
    }
    const pageView = this._pages[this._currentPageNumber - 1];
    
    
    const element = pageView.div;
    const view = {
      id: pageView.id,
      x: element.offsetLeft + element.clientLeft,
      y: element.offsetTop + element.clientTop,
      view: pageView,
    };
    return { first: view, last: view, views: [view] };
  }
  _getVisiblePages() {
    return getVisibleElements({
      scrollEl: this.container,
      views: this._pages,
      sortByVisibility: true,
      horizontal: this._isScrollModeHorizontal,
      rtl: this._isScrollModeHorizontal && this._isContainerRtl,
    });
  }
  /**
   * @param {number} pageNumber
   */
  isPageVisible(pageNumber) {