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.cancelRendering(keepAnnotations);
    this.renderingState = RenderingStates.INITIAL;
    const div = this.div;
    div.style.width = Math.floor(this.viewport.width) + "px";
    div.style.height = Math.floor(this.viewport.height) + "px";
    const childNodes = div.childNodes;
    const currentZoomLayerNode = (keepZoomLayer && this.zoomLayer) || null;
    const currentAnnotationNode =
      (keepAnnotations && this.annotationLayer?.div) || null;
    const currentXfaLayerNode = this.xfaLayer?.div || null;
    for (let i = childNodes.length - 1; i >= 0; i--) {
      const node = childNodes[i];
      if (
        currentZoomLayerNode === node ||
        currentAnnotationNode === node ||
        currentXfaLayerNode === node
      ) {
        continue;
      }
      div.removeChild(node);
    }
    div.removeAttribute("data-loaded");
    if (currentAnnotationNode) {