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.eventBus._off("textlayerrendered", this._onTextLayerRendered);
        this._onTextLayerRendered = null;
        if (!this.canvas) {
          return; 
        }
        this.pdfPage.getStructTree().then(tree => {
          if (!tree) {
            return;
          }
          if (!this.canvas) {
            return; 
          }
          const treeDom = this.structTreeLayer.render(tree);
          treeDom.classList.add("structTree");
          this.canvas.appendChild(treeDom);
        });
      };
      this.eventBus._on("textlayerrendered", this._onTextLayerRendered);
      this.structTreeLayer = this.structTreeLayerFactory.createStructTreeLayerBuilder(
        pdfPage
      );
    }
    div.setAttribute("data-loaded", true);
    this.eventBus.dispatch("pagerender", {
      source: this,
      pageNumber: this.id,
    });
    return resultPromise;
  }
  paintOnCanvas(canvasWrapper) {