It's actually not an atomic variable, just raw memory, so this is
technically not correct. However, the expert advice is to do this
until atomic_ref is available.

Change-Id: I4b74aa7123ed6ffeb2a06800c35b03e428861e80
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2270162
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68632}