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)

const currentTransform = currentCtx.mozCurrentTransform;
      if (group.matrix) {
        currentCtx.transform.apply(currentCtx, group.matrix);
      }
      if (!group.bbox) {
        throw new Error("Bounding box is required.");
      }
      
      
      let bounds = Util.getAxialAlignedBoundingBox(
        group.bbox,
        currentCtx.mozCurrentTransform
      );
      
      const canvasBounds = [
        0,
        0,
        currentCtx.canvas.width,
        currentCtx.canvas.height,
      ];
      bounds = Util.intersect(bounds, canvasBounds) || [0, 0, 0, 0];
      
      
      const offsetX = Math.floor(bounds[0]);
      const offsetY = Math.floor(bounds[1]);
      let drawnWidth = Math.max(Math.ceil(bounds[2]) - offsetX, 1);
      let drawnHeight = Math.max(Math.ceil(bounds[3]) - offsetY, 1);
      let scaleX = 1,
        scaleY = 1;
      if (drawnWidth > MAX_GROUP_SIZE) {