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.isViewerEmbedded) {
      
      return;
    }
    document.title = title;
  },
  get _docFilename() {
    
    
    return this._contentDispositionFilename || getPdfFilenameFromUrl(this.url);
  },
  /**
   * @private
   */
  _cancelIdleCallbacks() {
    if (!this._idleCallbacks.size) {
      return;
    }
    for (const callback of this._idleCallbacks) {
      window.cancelIdleCallback(callback);
    }
    this._idleCallbacks.clear();
  },
  /**
   * Closes opened PDF document.
   * @returns {Promise} - Returns the promise, which is resolved when all
   *                      destruction is completed.
   */
  async close() {