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.zoomLayer) {
      this.cssTransform(this.zoomLayer.firstChild);
    }
    this.reset( true,  true);
  }
  /**
   * PLEASE NOTE: Most likely you want to use the `this.reset()` method,
   *              rather than calling this one directly.
   */
  cancelRendering(keepAnnotations = false) {
    if (this.paintTask) {
      this.paintTask.cancel();
      this.paintTask = null;
    }
    this.resume = null;
    if (this.textLayer) {
      this.textLayer.cancel();
      this.textLayer = null;
    }
    if (!keepAnnotations && this.annotationLayer) {
      this.annotationLayer.cancel();
      this.annotationLayer = null;
    }
    if (this._onTextLayerRendered) {
      this.eventBus._off("textlayerrendered", this._onTextLayerRendered);
      this._onTextLayerRendered = null;
    }
  }
  cssTransform(target, redrawAnnotations = false) {