The implementation already exists, but the test doesn't.

R=titzer@chromium.org

Bug: v8:7581
Change-Id: I42e1b0a1c930ec4cc1f1701d5613828acab4fc30
Reviewed-on: https://chromium-review.googlesource.com/c/1426123Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59038}