Revert of cc: Use worker context for one-copy tile initialization.

Revert of cc: Use worker context for one-copy tile initialization. (patchset #20 id:380001 of https://codereview.chromium.org/1230203007/ )

Reason for revert:
Suspected of colliding with another patch and causing Issue 517719.

Original issue's description:
> cc: Use worker context for one-copy tile initialization.
>
> This moves management of staging resources to
> OneCopyTileTaskWorkerPool class. This makes it possible
> to use a worker context to issue and detect when copy
> operations complete.
>
> BUG=490295
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/d5157ac5afec145b85746b42f2d86383483a8222
> Cr-Commit-Position: refs/heads/master@{#342235}

TBR=piman@chromium.org,primiano@chromium.org,vmiura@chromium.org,vmpstr@chromium.org,reveman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=490295, 517719
Committed: https://crrev.com/78fd0255093c56d92b4281b7e3095a92a3f3d4ed
Cr-Commit-Position: refs/heads/master@{#342284}

[Ken Russell (switch to Gerrit), 2015-08-07 04:30:02]

Created Revert of cc: Use worker context for one-copy tile initialization.

[Ken Russell (switch to Gerrit), 2015-08-07 04:30:26]

The CQ bit was checked by kbr@chromium.org

[commit-bot: I haz the power, 2015-08-07 04:30:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1273163004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1273163004/1

[commit-bot: I haz the power, 2015-08-07 04:33:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-07 04:33:54]

Patchset 1 (id:??) landed as
https://crrev.com/78fd0255093c56d92b4281b7e3095a92a3f3d4ed
Cr-Commit-Position: refs/heads/master@{#342284}