Add task runners to more tests

Add task runners to more tests

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 base/ from MessageLoopProxy
over to ThreadTaskRunnerHandle, which requires an active task runner on
the current thread.

BUG=465354, 481632
TBR=tommi@chromium.org

Committed: https://crrev.com/f97a122208d5bd48d0200a83a585f005e8015353
Cr-Commit-Position: refs/heads/master@{#327463}

[Sami, 2015-04-28 18:40:35]

skyostil@chromium.org changed reviewers:
+ jochen@chromium.org

[Sami, 2015-04-28 18:41:03]

skyostil@chromium.org changed reviewers:
+ tommi@chromium.org

[Sami, 2015-04-28 18:41:15]

PTAL.

[jochen (gone - plz use gerrit), 2015-04-28 19:01:07]

lgtm

[Sami, 2015-04-29 08:55:11]

Thanks Jochen. TBR'ing since the media change is pretty trivial.

[Sami, 2015-04-29 08:55:17]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2015-04-29 08:55:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1105373002/80001

[commit-bot: I haz the power, 2015-04-29 09:59:49]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-04-29 10:00:38]

Patchset 5 (id:??) landed as
https://crrev.com/f97a122208d5bd48d0200a83a585f005e8015353
Cr-Commit-Position: refs/heads/master@{#327463}