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)

let isScalingRestricted = false;
    if (this.canvas && this.maxCanvasPixels > 0) {
      const outputScale = this.outputScale;
      if (
        ((Math.floor(this.viewport.width) * outputScale.sx) | 0) *
          ((Math.floor(this.viewport.height) * outputScale.sy) | 0) >
        this.maxCanvasPixels
      ) {
        isScalingRestricted = true;
      }
    }
    if (this.canvas) {
      if (
        this.useOnlyCssZoom ||
        (this.hasRestrictedScaling && isScalingRestricted)
      ) {
        this.cssTransform(this.canvas, true);
        this.eventBus.dispatch("pagerendered", {
          source: this,
          pageNumber: this.id,
          cssTransform: true,
          timestamp: performance.now(),
          error: this._renderError,
        });
        return;
      }
      if (!this.zoomLayer && !this.canvas.hidden) {
        this.zoomLayer = this.canvas.parentNode;
        this.zoomLayer.style.position = "absolute";
      }