Ensures that there is no concurrent allocation happening.

Bug: v8:10315
Change-Id: Ief40cbde9d859e3a2eea66d6e4437d7f0e3840e8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2418951Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69998}