Revert of Use a single CGLContextObj to draw and update the IOSurface

Revert of Use a single CGLContextObj to draw and update the IOSurface (patchset #4 id:60001 of https://codereview.chromium.org/627003002/)

Reason for revert:
I hear reports of instability on Mac try servers, with crashes in the GL driver.

Original issue's description:
> Use a single CGLContextObj to draw and update the IOSurface
>
> There is no reason that this can't be done, based on documentation,
> but it may be that this will cause crashes during texture destruction
> or context tear-down (see crbug.com/411782).
>
> I have 3 theories as to why these crashes are occurring
> 1. Using an IOSurface in a CGLContextObj that is also used by a
>    CAOpenGLLayer causes bugs
> 2. The crashes observed were because context destruction just crashes
>    at a certain frequency, and previous patches made context destruction
>    more frequent.
> 3. IOSurface-backed textures should be immutable -- no GL texture
>    should be bound to one IOSurface then the other.
>
> If theory 1 is correct, this will need to be reverted because the crashes
> will re-occur. If theories 2 or 3 are correct, then this patch is safe.
>
> BUG=420253
>
> Committed: https://crrev.com/0ea6e165293b7d24deec0d29fb9d6333d3a71b6d
> Cr-Commit-Position: refs/heads/master@{#298916}

TBR=kbr@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=420253
Committed: https://crrev.com/4f30f97aa5185a61a3359fa55770b3dc64d62ea1
Cr-Commit-Position: refs/heads/master@{#298969}

[ccameron, 2014-10-09 20:35:45]

Created Revert of Use a single CGLContextObj to draw and update the IOSurface

[commit-bot: I haz the power, 2014-10-09 20:36:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/647553002/1

[commit-bot: I haz the power, 2014-10-09 20:37:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-09 20:38:45]

Patchset 1 (id:??) landed as
https://crrev.com/4f30f97aa5185a61a3359fa55770b3dc64d62ea1
Cr-Commit-Position: refs/heads/master@{#298969}