Revert of [es6] ship Object.assign

Revert of [es6] ship Object.assign (patchset #2 id:20001 of https://codereview.chromium.org/1191003003/)

Reason for revert:
Seems to break asan somehow

Original issue's description:
> [es6] ship Object.assign
>
> BUG=v8:4007
> LOG=N
> R=rossberg@chromium.org, arv@chromium.org
> CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/12e194860a56d47a10d89ae34761a4af6b6166bb
> Cr-Commit-Position: refs/heads/master@{#29118}

TBR=arv@chromium.org,dslomov@chromium.org,rossberg@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4007
Committed: https://crrev.com/95a3bc965ed80186215cea788caa5faae0898839
Cr-Commit-Position: refs/heads/master@{#29124}

[caitp (gmail), 2015-06-18 18:55:54]

Created Revert of [es6] ship Object.assign

[commit-bot: I haz the power, 2015-06-18 18:56:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1191593005/1

[commit-bot: I haz the power, 2015-06-18 18:56:15]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-18 18:56:16]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[rossberg, 2015-06-18 19:08:10]

lgtm

[caitp (gmail), 2015-06-18 19:14:56]

The CQ bit was checked by caitpotter88@gmail.com

[commit-bot: I haz the power, 2015-06-18 19:15:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1191593005/1

[commit-bot: I haz the power, 2015-06-18 19:15:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-18 19:15:47]

Patchset 1 (id:??) landed as
https://crrev.com/95a3bc965ed80186215cea788caa5faae0898839
Cr-Commit-Position: refs/heads/master@{#29124}