The same thing happened to my partner when he was young. Pretty much exactly the same type of attack, from his right eye down through his lip. Hopefully this boy will heal as well as his face did, you can see the scars but not majorly bad.
Don't get me wrong I love dogs, but it has really put me off labs, considering it was a lab with my DP too.
Labs are thought to be the biggest perpetrator in terms of bites to children/adults. I don't think this is because they are a dangerous, just that they are so popular with families, so there are more of them.
This is no such thing as a dangerous breed, only dangerous owners.
I do hope the boy recovers and is not psychologically damaged too.