Melvin Gordon cares, OK? Maybe too much, but he cares. I mean, would a guy who didn’t give a patootie play the second half of an absolute slugfest between the Broncos and San Francisco 49ers without a working chin strap? “You know it’s gonna be helmet-to-helmet. I was out there (and) the chin strap broke,” Gordon recalled with a smile after his game-winning touchdown lifted the Broncos to an ugly-but-memorable 11-10 win over San Francisco Sunday night. “I was like, ‘I ain’t getting out of this (expletive) game. I gotta go. I gotta go. I gotta go.’ I was like,…