R=titzer@chromium.org

Bug: v8:6600
Change-Id: Id2bd29b89a0db47d7e9ea957521df1558baa6e4a
Reviewed-on: https://chromium-review.googlesource.com/926201
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51422}