When the TypedArray iterator constructor code path was added, a technically
incorrect optimization was added which uses the arraylike code path on array
arguments, even though the %ArrayIterator% could have been monkey-patched
to give different behavior. A previous patch removed this optimization, and
this patch restores it due to the huge performance regression that resulted.

The optimization was previously removed in
https://codereview.chromium.org/1767893002

BUG=chromium:593644
R=adamk
LOG=Y

Review URL: https://codereview.chromium.org/1779373002

Cr-Commit-Position: refs/heads/master@{#34697}