This helper is used directly when constructing from an object with
a length, as well as by ConstructByIterable and ByTypedArray.

BUG=v8:5977

Change-Id: I18a4829c2a22a6099cf3b0824ea1f698bfbf1917
Reviewed-on: https://chromium-review.googlesource.com/456707Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Franziska Hinkelmann <franzih@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44116}