Base: Truncate the timeout of WaitableEvent::TimedWait on Windows.

The timeout has to be adjusted to milliseconds (the resolution of the
underlying call), but it should be truncated instead of extended,
because the documentation clearly states that the function can fail in
less time than the passed-in timeout, and by definition, the timeout
is the maximum time that the caller is willing to block.

BUG=none

Review URL: https://codereview.chromium.org/1040833002

Cr-Commit-Position: refs/heads/master@{#323178}
1 file changed