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
Initializing nsSystemInfo can't be done off the main thread on
Windows, and we can't guarantee that it has been initialized before
calling this code.
MozReview-Commit-ID: DRNCrakNMmH