This field is dead since https://chromium-review.googlesource.com/c/v8/v8/+/916261, but got
accidentally added back by https://chromium-review.googlesource.com/c/v8/v8/+/919481 due to
a bad merge.

BUG=v8:5203,chromium:817258

Change-Id: Id6f06de84de7dcd4e6d467edf28974912ad33571
Reviewed-on: https://chromium-review.googlesource.com/948849Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51738}