Revert of Add WeakMap to v8.h

Revert of Add WeakMap to v8.h (patchset #3 id:40001 of https://codereview.chromium.org/886473005/)

Reason for revert:
Broke compilation on component build http://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20nosnap%20-%20shared/builds/5007/steps/compile/logs/stdio

Original issue's description:
> Add WeakMap to v8.h
>
> A new map wich references its keys weakly is added to v8.h. Internally it uses the same storage as JSWeakMap but doesn't depend on the JavaScript part of WeakMap implementation in weak-collection.js, hence it can be instantiated without entering any context.
>
> BUG=chromium:437416
> LOG=Y
>
> Committed: https://crrev.com/37d4c57630636f21e3add8d3d1c7c978ff5fc8e0
> Cr-Commit-Position: refs/heads/master@{#26401}

TBR=jochen@chromium.org,mstarzinger@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:437416
Committed: https://crrev.com/aeec653f49b09fb4cda3f7b1090a7baf214c7795
Cr-Commit-Position: refs/heads/master@{#26402}

[yurys, 2015-02-03 14:41:29]

Created Revert of Add WeakMap to v8.h

[commit-bot: I haz the power, 2015-02-03 14:42:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/898763002/1

[commit-bot: I haz the power, 2015-02-03 14:42:40]

Committed patchset #1 (id:1)

[Michael Starzinger, 2015-02-03 14:42:49]

LGTM (rubber-stamped).

[commit-bot: I haz the power, 2015-02-03 14:42:55]

Patchset 1 (id:??) landed as
https://crrev.com/aeec653f49b09fb4cda3f7b1090a7baf214c7795
Cr-Commit-Position: refs/heads/master@{#26402}