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)

bounds,
          scale,
          coords,
          colors,
          figures,
          shadingFill ? null : background,
          owner.cachedCanvases,
          owner.webGLContext
        );
        if (!shadingFill) {
          ctx.setTransform.apply(ctx, owner.baseTransform);
          if (matrix) {
            ctx.transform.apply(ctx, matrix);
          }
        }
        ctx.translate(
          temporaryPatternCanvas.offsetX,
          temporaryPatternCanvas.offsetY
        );
        ctx.scale(temporaryPatternCanvas.scaleX, temporaryPatternCanvas.scaleY);
        return ctx.createPattern(temporaryPatternCanvas.canvas, "no-repeat");
      },
    };
  },
};
ShadingIRs.Dummy = {
  fromIR: function Dummy_fromIR() {
    return {
      getPattern: function Dummy_fromIR_getPattern() {
        return "hotpink";