Revert of Fix memory leak caused by field type in descriptor array.

Revert of Fix memory leak caused by field type in descriptor array. (patchset #3 id:40001 of https://codereview.chromium.org/955063002/)

Reason for revert:
Breaks test/mjsunit/debug-clearbreakpointgroup.js on arm64.debug.

Original issue's description:
> Fix memory leak caused by field type in descriptor array.
>
> When a field type is a map, it is wrapped in a weak cell upon storing to the descriptor array.
>
> Map::GetFieldType(i) does the unwrapping.
>
> BUG=v8:3877
> LOG=N
> TEST=cctest/test-heap/Regress3877
>
> Committed: https://crrev.com/77d3ae0e119893ac8d34ea6ca090cddd5bbf987e
> Cr-Commit-Position: refs/heads/master@{#26879}

TBR=verwaest@chromium.org,ulan@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:3877
Committed: https://crrev.com/b57be748b175695be2507cedf3423b59b9d6cd20
Cr-Commit-Position: refs/heads/master@{#26883}

[marja, 2015-02-26 14:45:25]

Created Revert of Fix memory leak caused by field type in descriptor array.

[commit-bot: I haz the power, 2015-02-26 14:45:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/960103003/1

[commit-bot: I haz the power, 2015-02-26 14:46:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-26 14:46:18]

Patchset 1 (id:??) landed as
https://crrev.com/b57be748b175695be2507cedf3423b59b9d6cd20
Cr-Commit-Position: refs/heads/master@{#26883}