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.startCleanup(keepLoadedFonts || this.isPureXfa);
  }
  /**
   * Destroys the current document instance and terminates the worker.
   */
  destroy() {
    return this.loadingTask.destroy();
  }
  /**
   * @type {DocumentInitParameters} A subset of the current
   *   {DocumentInitParameters}, which are either needed in the viewer and/or
   *   whose default values may be affected by the `apiCompatibilityParams`.
   */
  get loadingParams() {
    return this._transport.loadingParams;
  }
  /**
   * @type {PDFDocumentLoadingTask} The loadingTask for the current document.
   */
  get loadingTask() {
    return this._transport.loadingTask;
  }
  /**
   * @returns {Promise<Uint8Array>} A promise that is resolved with a
   *   {Uint8Array} containing the full data of the saved document.
   */
  saveDocument() {