With the previous changes the builtin would take the slow path for
JSArray's when the iterator was already exhausted (i.e. the internal
[[ArrayIteratorNextIndex]] field contains 2^32-1 as HeapNumber), even
though that could also be handled in the fast path. This changes the
handling such that the three distinct cases (if_array, if_other and
if_typedarray) are really distinct, and all JSArray's are always
handled by the if_array case.

Bug: v8:7510, v8:7514, v8:8070, chromium:876654
Change-Id: I1636b0616645f9e99f34f851df410992653cb380
Reviewed-on: https://chromium-review.googlesource.com/1186403Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55341}