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)

this.destroyed = true;
      const transportDestroyed = !this._transport
        ? Promise.resolve()
        : this._transport.destroy();
      return transportDestroyed.then(() => {
        this._transport = null;
        if (this._worker) {
          this._worker.destroy();
          this._worker = null;
        }
      });
    }
  }
  return PDFDocumentLoadingTask;
})();
/**
 * Abstract class to support range requests file loading.
 */
class PDFDataRangeTransport {
  /**
   * @param {number} length
   * @param {Uint8Array} initialData
   * @param {boolean} [progressiveDone]
   * @param {string} [contentDispositionFilename]
   */
  constructor(