Summary:
Our existing `timeout` implementation was always throwing an exception, due to sleeping and then throw an exception, which is than handled but ignored by `Promise.race`.
This implementation has a few problems
1. Because it always throws, having a debugger session with 'break on caught exceptions' will pause on every usage of timeout (rather than just the ones that actually timeout). This makes this way of debugging a bit useless.
2. Throwing exceptions is in principle an expensive process (due to the stack trace generation)
3. Not cancelling the timeout used by sleep is a bit of a waste as well
Reviewed By: lawrencelomax
Differential Revision: D33982717
fbshipit-source-id: d739c02112e1c1bc4cd691af852371d08a99abc6
e4a3696fd5