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.clearRect(0, 0, newWidth, newHeight);
        tmpCtx.drawImage(
          imgToPaint,
          0,
          0,
          paintWidth,
          paintHeight,
          0,
          0,
          newWidth,
          newHeight
        );
        imgToPaint = tmpCanvas.canvas;
        paintWidth = newWidth;
        paintHeight = newHeight;
        tmpCanvasId = tmpCanvasId === "prescale1" ? "prescale2" : "prescale1";
      }
      ctx.drawImage(
        imgToPaint,
        0,
        0,
        paintWidth,
        paintHeight,
        0,
        -height,
        width,
        height
      );
      if (this.imageLayer) {
        const position = this.getCanvasPosition(0, -height);