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._buffer.push(pageView);
    };
    this.eventBus._on("pagerender", this._onBeforeDraw);
    this._onAfterDraw = evt => {
      if (evt.cssTransform || this._onePageRenderedCapability.settled) {
        return;
      }
      this._onePageRenderedCapability.resolve();
      this.eventBus._off("pagerendered", this._onAfterDraw);
      this._onAfterDraw = null;
    };
    this.eventBus._on("pagerendered", this._onAfterDraw);
    
    
    firstPagePromise
      .then(firstPdfPage => {
        this._firstPageCapability.resolve(firstPdfPage);
        this._optionalContentConfigPromise = optionalContentConfigPromise;
        const scale = this.currentScale;
        const viewport = firstPdfPage.getViewport({ scale: scale * CSS_UNITS });
        const textLayerFactory =
          this.textLayerMode !== TextLayerMode.DISABLE ? this : null;
        const xfaLayerFactory = isPureXfa ? this : null;
        for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
          const pageView = new PDFPageView({
            container: this._viewerElement,
            eventBus: this.eventBus,