Objects allocated on the background thread during incremental marking, need to be allocated black. This prevents concurrent marking to observe uninitialized objects.

Bug: v8:10315
Change-Id: Ia4b05a2a72e4142c79b31a01cbf162a6599a18c0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2196347
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67967}