We want to spin for faster response, but we only want to spin for a very short time.
If we're waiting for a while, we don't want to be burning CPU for the entire time.
Therefore, only spin for 30 ms, then fall back to waiting on an event.
MozReview-Commit-ID: ErAIwpsIqYz
--HG--
extra : rebase_source : b6ac024adb7853456fd06c4385cf32184c8aeca2