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)

.then(([transparency, optionalContentConfig]) => {
        if (this.pendingCleanup) {
          complete();
          return;
        }
        if (this._stats) {
          this._stats.time("Rendering");
        }
        internalRenderTask.initializeGraphics({
          transparency,
          optionalContentConfig,
        });
        internalRenderTask.operatorListChanged();
      })
      .catch(complete);
    return renderTask;
  }
  /**
   * @returns {Promise<PDFOperatorList>} A promise resolved with an
   *   {@link PDFOperatorList} object that represents page's operator list.
   */
  getOperatorList() {
    function operatorListChanged() {
      if (intentState.operatorList.lastChunk) {
        intentState.opListReadCapability.resolve(intentState.operatorList);
        intentState.renderTasks.delete(opListTask);
      }
    }
    const renderingIntent = "oplist";
    let intentState = this._intentStates.get(renderingIntent);