In 15w31c if you put a head in your inventory hotbar it shows up bigger then the 1.8.8 and you can see its chin in your hand in 15w31c but in 1.8.8 you can and also if this was just a feature I don't totally like it because if you do f5 you just see the head as it use to be then you push f5 to get back to 1st person then its bigger and it doesn't look the same way that your holding it then in 1st person veiw
This is not bug. Because head bigger is more easy to see who is or what is mob