The assert-guarded comment claiming that ToNumber could not
possibly neuter the target array unfortunately turns out to
have been wishful thinking.

Bug: chromium:816961
Change-Id: Ib98f96f4cd7f33414c0b5a6037bfb881938cc15e
Reviewed-on: https://chromium-review.googlesource.com/939767
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51637}