Chocolate speedway is a gay sex slang term. I just saw that on urbandictionary.com.
They've picked up on it have they? It's not a gay term, it's a non gay term to describe a particular act. It tends to be used by people who are interested in gay sex more for its comic potential than anything else.
It has a rich seam of comic potential, and you've just scratched the surface. Have you investigated any of the other jobtitles. I can post a few more if you want. How about Donkey Milker, Salad Dodger, Bunny Shooter, Sour Apple Quickstepper? Clue: None of them are gay.
I've only been on the urban dictionary a little bit. It's very good for American slang.