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.getOutline();
  }
  /**
   * @returns {Promise<OptionalContentConfig>} A promise that is resolved with
   *   an {@link OptionalContentConfig} that contains all the optional content
   *   groups (assuming that the document has any).
   */
  getOptionalContentConfig() {
    return this._transport.getOptionalContentConfig();
  }
  /**
   * @returns {Promise<Array<number> | null>} A promise that is resolved with
   *   an {Array} that contains the permission flags for the PDF document, or
   *   `null` when no permissions are present in the PDF file.
   */
  getPermissions() {
    return this._transport.getPermissions();
  }
  /**
   * @returns {Promise<{ info: Object, metadata: Metadata }>} A promise that is
   *   resolved with an {Object} that has `info` and `metadata` properties.
   *   `info` is an {Object} filled with anything available in the information
   *   dictionary and similarly `metadata` is a {Metadata} object with
   *   information from the metadata section of the PDF.
   */
  getMetadata() {