Revert of Add d8 API for spawning function on a new thread. (patchset #6 id:100001...

Revert of Add d8 API for spawning function on a new thread. (patchset #6 id:100001 of https://codereview.chromium.org/1185643004/)

Reason for revert:
Fails on V8 Win32 - nosnap - shared (http://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20nosnap%20-%20shared/builds/7427)

Fails on V8 Arm - debug builder (http://build.chromium.org/p/client.v8/builders/V8%20Arm%20-%20debug%20builder/builds/4361)

Fails on V8 Linux - shared (http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20shared/builds/4430)

Original issue's description:
> Add d8 API for spawning function on a new thread.
>
> This API closely matches the Worker API. The differences:
>
> 1) The argument to the Worker constructor is a function to run, not a script.
> 2) Receiving a message from a worker is a synchronous API (as there is no event
> loop).
>
> The serialization done here is not robust as the real DOM implementation. For
> example, recursive data structures or otherwise duplicated objects are not
> allowed.
>
> BUG=none
> R=jochen@chromium.org
> LOG=n
>
> Committed: https://crrev.com/3d98b956b56fa283b40913788ff760022d478812
> Cr-Commit-Position: refs/heads/master@{#29126}

TBR=jochen@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=none

Review URL: https://codereview.chromium.org/1192193002

Cr-Commit-Position: refs/heads/master@{#29130}