They were introduced in https://crrev.com/c/559674, but never used.

R=neis@chromium.org

Bug: v8:8834
Change-Id: I773bc1ba14c7a1d5adc1a483f539221f18042361
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1578505Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60965}