... when we do have an isolate. This is a little leaner.

Change-Id: Ia95d9888b11cab9e43362f4fe78689a79dfa8b2d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2964604
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75181}