Ensure tests have an active task runner
This patch modifies a number of tests to have a more realistic threading set-up by either:
a) adding a TestBrowserThreadBundle
b) constructing any existing TestBrowserThreadBundle earlier or
c) adding a MessageLoop as appropriate.
This makes it possible to later migrate ipc/ from MessageLoopProxy over to
ThreadTaskRunnerHandle, which requires an active task runner on the current thread.
BUG=465354
TBR=sievers@chromium.org
Review URL: https://codereview.chromium.org/
1128873012
Cr-Commit-Position: refs/heads/master@{#329146}