In ArrayBuiltinsAssembler::VisitAllFastElementsOneKind(), we enumerate
an arrays elements, carefully checking for the "hole" when required.
This code is only called for arrays whose prototype is the initial array
prototype. And the path is only available when the initial array
prototype is free of elements. Since that's the case, we only need to
verify that the initial array prototype remains free of elements during
an iteration with javascript callbacks. We don't need a body of code
that can walk the prototype chain looking for elements visible through
the "hole" value. In practice, this code was never run.

Change-Id: Iba5e275c559d495aa1cf6a4f29d66e2ce475c981
Reviewed-on: https://chromium-review.googlesource.com/1015023
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52660}