Revert of Reland: Lazily initialize MessageLoop for faster thread startup

Revert of Reland: Lazily initialize MessageLoop for faster thread startup (patchset #5 id:160001 of https://codereview.chromium.org/1129953004/)

Reason for revert:
Massive data race reports, see https://crbug.com/489263

Original issue's description:
> Reland: Lazily initialize MessageLoop for faster thread startup
>
> Original review: https://codereview.chromium.org/1011683002/
>
> Reverted because it's suspected for following flakiness issues:
> http://crbug.com/485157 - Windows race
> http://crbug.com/485091 - Android ThreadWatcher
> http://crbug.com/485178 - interactive_ui_tests Menu* tests
>
> PS1 is the original patch set that gets reverted.
>
> BUG=465458, 485157, 485091, 485178
> TBR=jam
>
> Committed: https://crrev.com/8b6133a69f16702a32a3c3104630c4d9ac393b7a
> Cr-Commit-Position: refs/heads/master@{#330329}

TBR=thakis@chromium.org,toyoshim@chromium.org,jam@chromium.org,kinuko@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=465458, 485157, 485091, 485178
Committed: https://crrev.com/787e3347eb49a59db5e6fe0374f50464f36d48e3
Cr-Commit-Position: refs/heads/master@{#330351}

[Alexander Potapenko, 2015-05-18 13:23:19]

Created Revert of Reland: Lazily initialize MessageLoop for faster thread
startup

[commit-bot: I haz the power, 2015-05-18 13:23:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140363002/1

[commit-bot: I haz the power, 2015-05-18 13:24:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-18 13:25:12]

Patchset 1 (id:??) landed as
https://crrev.com/787e3347eb49a59db5e6fe0374f50464f36d48e3
Cr-Commit-Position: refs/heads/master@{#330351}