I noticed while profiling calls to TimeUntilNextProcess.
It's benign, but the implementation seems to be done to accomodate the
test rather than the other way around, so I'm making the test behave
more like a ProcessThread would.
BUG=None
Review-Url: https://codereview.webrtc.org/2715133002
Cr-Commit-Position: refs/heads/master@{#16867}