In certain corner-cases we would grow a FAST_ELEMENTS packed backing store of a
JS_ARGUMENTS_TYPE object without converting to holey elements kinds. As a side
effect you could then read out the_hole.
BUG=v8:5772
Review-Url: https://codereview.chromium.org/2597013004
Cr-Commit-Position: refs/heads/master@{#41921}
