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.getPageLabels();
  }
  /**
   * @returns {Promise<string>} A promise that is resolved with a {string}
   *   containing the page layout name.
   */
  getPageLayout() {
    return this._transport.getPageLayout();
  }
  /**
   * @returns {Promise<string>} A promise that is resolved with a {string}
   *   containing the page mode name.
   */
  getPageMode() {
    return this._transport.getPageMode();
  }
  /**
   * @returns {Promise<Object | null>} A promise that is resolved with an
   *   {Object} containing the viewer preferences, or `null` when no viewer
   *   preferences are present in the PDF file.
   */
  getViewerPreferences() {
    return this._transport.getViewerPreferences();
  }
  /**
   * @returns {Promise<any | null>} A promise that is resolved with an {Array}
   *   containing the destination, or `null` when no open action is present
   *   in the PDF.
   */
  getOpenAction() {