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)

tmpCtx = tmpCanvas.context;
        putBinaryImageData(tmpCtx, imgData, this.current.transferMaps);
        imgToPaint = tmpCanvas.canvas;
      }
      let paintWidth = width,
        paintHeight = height;
      let tmpCanvasId = "prescale1";
      
      
      
      while (
        (widthScale > 2 && paintWidth > 1) ||
        (heightScale > 2 && paintHeight > 1)
      ) {
        let newWidth = paintWidth,
          newHeight = paintHeight;
        if (widthScale > 2 && paintWidth > 1) {
          newWidth = Math.ceil(paintWidth / 2);
          widthScale /= paintWidth / newWidth;
        }
        if (heightScale > 2 && paintHeight > 1) {
          newHeight = Math.ceil(paintHeight / 2);
          heightScale /= paintHeight / newHeight;
        }
        tmpCanvas = this.cachedCanvases.getCanvas(
          tmpCanvasId,
          newWidth,
          newHeight
        );
        tmpCtx = tmpCanvas.context;