Revert of Implement V8Platform::CallDelayedOnForegroundThread.

Revert of Implement V8Platform::CallDelayedOnForegroundThread. (patchset #2 id:20001 of https://codereview.chromium.org/1181113003/)

Reason for revert:
We need to first roll V8 with empty implementation of the function and then use "override" here.

The trick with "virtual" does not work because chromium style checks for "override".

Original issue's description:
> Implement V8Platform::CallDelayedOnForegroundThread.
>
> The corresponding change on V8 side: https://codereview.chromium.org/1179153002
>
> BUG=490559
>
> Committed: https://crrev.com/06c3d1b9b782c2bdb3a4e121819351f95804cea5
> Cr-Commit-Position: refs/heads/master@{#334592}

TBR=jochen@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=490559
Committed: https://crrev.com/f4f00c7a28bb5786f5dce52acf4e8bd2d39df6a2
Cr-Commit-Position: refs/heads/master@{#334794}

[ulan, 2015-06-17 09:05:46]

Created Revert of Implement V8Platform::CallDelayedOnForegroundThread.

[commit-bot: I haz the power, 2015-06-17 09:06:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1186173005/1

[commit-bot: I haz the power, 2015-06-17 09:07:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-17 09:08:30]

Patchset 1 (id:??) landed as
https://crrev.com/f4f00c7a28bb5786f5dce52acf4e8bd2d39df6a2
Cr-Commit-Position: refs/heads/master@{#334794}