R=rossberg@chromium.org

Bug: v8:6651
Change-Id: Iaa9217cacded9bdd3f0a35775275e79c231c272a
Reviewed-on: https://chromium-review.googlesource.com/642969Reviewed-by: Andreas Rossberg <rossberg@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47709}