Revert of Move AW renderer compositor context to gpu thread

Revert of Move AW renderer compositor context to gpu thread (patchset #6 id:100001 of https://codereview.chromium.org/769703005/)

Reason for revert:
Suspect causing AwContentsClientFullScreenTest#testPowerSaveBlockerIsTransferredToFullscreen to time out

Original issue's description:
> Move AW renderer compositor context to gpu thread
>
> Use TexSubImage2D instead of TexImage2D to avoid orphaning
> EGLImage
> Create the renderer compositor context on the gpu thread.
>
> BUG=448168, 259924
>
> Committed: https://crrev.com/a4baed454be2bb165cb12eb7df432e9138e746e6
> Cr-Commit-Position: refs/heads/master@{#313846}

TBR=epenner@chromium.org,sievers@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=448168, 259924
Committed: https://crrev.com/2c2d394395524bc05c057bfeba2c725c7908d6dc
Cr-Commit-Position: refs/heads/master@{#313948}

[boliu, 2015-01-30 18:23:45]

Created Revert of Move AW renderer compositor context to gpu thread

[commit-bot: I haz the power, 2015-01-30 18:24:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/888903002/1

[commit-bot: I haz the power, 2015-01-30 18:25:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-30 18:27:24]

Patchset 1 (id:??) landed as
https://crrev.com/2c2d394395524bc05c057bfeba2c725c7908d6dc
Cr-Commit-Position: refs/heads/master@{#313948}