It caused crashes in the extension process on Canary.

This reverts commit b6059a67.

Also revert followup test CL:

  "[api] Add test for EnumeratorCallback and for...in."

as it depends on the logic in the reverted change.

This reverts commit 56772de7.

Bug: chromium:757371, v8:6627
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Id110128e6dc858a5a60ffc0175e8bb927b90bfc5
Reviewed-on: https://chromium-review.googlesource.com/626720Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47522}