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)

return this._transport.getPageIndex(ref);
  }
  /**
   * @returns {Promise<Object<string, Array<any>>>} A promise that is resolved
   *   with a mapping from named destinations to references.
   *
   * This can be slow for large documents. Use `getDestination` instead.
   */
  getDestinations() {
    return this._transport.getDestinations();
  }
  /**
   * @param {string} id - The named destination to get.
   * @returns {Promise<Array<any>>} A promise that is resolved with all
   *   information of the given named destination.
   */
  getDestination(id) {
    return this._transport.getDestination(id);
  }
  /**
   * @returns {Promise<Array<string> | null>} A promise that is resolved with
   *   an {Array} containing the page labels that correspond to the page
   *   indexes, or `null` when no page labels are present in the PDF file.
   */
  getPageLabels() {