Bug 1101397 - Clear up unnecessary checking of "undefined" DOMString attribute. r=echen
Bug 1107329 - Add locks tasks queue vivacity checking. r=qdot

To help diagnosing further issues with the Settings API getting blocked,
we add some tracking of the tasks and locks queue vivacity. We ensure to
keep track of the last lock id at the head of the queue, and we verify
whether it does not stays on top of it for too long.
Bug 1111970 - Use gateways[0] instead of gateway. r=vchang
Bug 1113199 - Settings OOP Tests for Bug 1110872. r=gerard-majax