The impl works by posting up to NumberOfWorkerThreads() tasks
with CallOnWorkerThread().

Change-Id: I188ac57c9e5d6e3befdcc6f945fbf337dabe1d1d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2130886
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67368}