Small notice for anyone poking around in here: 

The brown_mooshroom.png and red_mooshroom.png located here are not actually used at all because of a couple limitations.
The actual textures rendered are in assets\minecraft\textures\entity\cow and the custom texture is located in an empty space inside the original texture so ETF + EMF/Optifine are not a required feature.
These are simply the custom texture on their own for convenience for us and anyone else poking around in here (Hence it's inclusion in the release version).