If a method happens on the main thread and only on the main thread
(i.e. it will never be run on the background), it is safer to use
non-atomic accessors as TSAN will give warnings if we use them
improperly.

As a drive-by, pass the isolate as a parameter where it was readily
available as it saves us from getting the isolate from the object later
on.

Bug: v8:7790
Change-Id: Id9bdd69254edc60b0331a32fccf1479a95b7d286
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2732669Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73251}