GitLab

Only logic change is that base::Thread will run all tasks before being
destroyed (as opposed to previous SKIP_ON_SHUTDOWN semantics), but no
tests called Shutdown() explicitly so I assume this wasn't an explicit
choice and that those tests don't care?

A few drive-by cleanups too.

BUG=646443
NO_DEPENDENCY_CHECKS=true

Review-Url: https://codereview.chromium.org/2334163005
Cr-Commit-Position: refs/heads/master@{#418912}