That dep file was submitted by a user who said firefox wouldn't start with the dep file like it was, though there were no new real dependencies in the submitted dep file as recursion resolved all needed ones. I saw the typo and thought I fixed it. The user first stated he was using TC 2.10, but later realized it was 2.9. I was going to revert the dep file but was not in a huge rush as I thought the typo was not there.
Oh well, stuff happens.