This makes the deoptimizer happy, and is more consistent with other
Torque JS functions.

BUG=chromium:912504, v8:8021
R=tebbi@chromium.org, danno@chromium.org, mvstanton@chromium.org, gsathya@chromium.org

Change-Id: I4c86db9549c367dfab7f76b49a0cf3c69d3ec50b
Reviewed-on: https://chromium-review.googlesource.com/c/1366397
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58161}