Revert of Make Reflector Use Main Thread MessageLoop when in SingleThread

Revert of Make Reflector Use Main Thread MessageLoop when in SingleThread (patchset #1 id:1 of https://codereview.chromium.org/899073003/)

Reason for revert:
Reason for revert:
Speculatively reverting to try to fix broken Mac 10.8 retina layout tests in Blink:
compositing/iframes/iframe-composited-scrolling-hide-and-show.html
compositing/iframes/overlapped-iframe-iframe.html
svg/as-border-image/svg-as-border-image-2.html
and more.

Original issue's description:
> Make Reflector Use Main Thread MessageLoop when in SingleThread
>
> When in using single thread with browser compositor, make reflector use
> main thread MessageLoop instead.
>
> Test with forced SW mirrored display on both Linux-cros build and Pixel.
> BUG=453732
>
> Committed: https://crrev.com/0b88b2372f1ad82c12656a4b9a17098470e576a1
> Cr-Commit-Position: refs/heads/master@{#314665}

TBR=danakj@chromium.org,weiliangc@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=453732
Committed: https://crrev.com/6cb534f690545ebda6751d153a6e72f50d4003cc
Cr-Commit-Position: refs/heads/master@{#314732}

[dcheng, 2015-02-05 03:14:36]

Created Revert of Make Reflector Use Main Thread MessageLoop when in
SingleThread

[commit-bot: I haz the power, 2015-02-05 03:15:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/900133002/1

[commit-bot: I haz the power, 2015-02-05 03:16:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-05 03:17:03]

Patchset 1 (id:??) landed as
https://crrev.com/6cb534f690545ebda6751d153a6e72f50d4003cc
Cr-Commit-Position: refs/heads/master@{#314732}

[dcheng, 2015-02-05 04:03:01]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/896393002/ by dcheng@chromium.org.

The reason for reverting is: These aren't the changes you're looking for..