We didn't check if the input typed array was neutered before going to
the fast path, so we hit a CHECK in this case.

Fix this by just checking if the buffer was neutered and then going to
the 'check iterator' case if it is. This will cause a TypeError via
IterableToList, which was the same as the behavior before the
optmization was landed.

Bug: chromium:899519
Change-Id: I09e6389ea2ab1e3bef01e616721b48a9b66c1b2a
Reviewed-on: https://chromium-review.googlesource.com/c/1307422
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57137}