If we're going to use WebP anyway, we might as well drop PNG too in favor of the lossless mode. I don't know of any downsides to this. But mandatory chroma subs

If we're going to use WebP anyway, we might as well drop PNG too in favor of the lossless mode. I don't know of any downsides to this. But mandatory chroma subsampling means WebP can't completely replace JPEG.