in preparation for incrementally transitioning their subclasses.

Bug: v8:3770
Change-Id: I5ed6adb1969bc1ec7125571fea443834ca255c22
Reviewed-on: https://chromium-review.googlesource.com/c/1377453
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58252}