Currently the concurrent marker visits any fixed array in one go
ignoring the progress bar and does not expect seeing black arrays
in the worklist. For this reason, if the main thread marker starts
visiting a large array with the progress bar, then it has to re-push
the array in the bailout worklist. So all subsequent visitations of
the array happen on the main thread.

This patch makes the progress bar thread-safe and allows the
concurrent marker to visit arrays in chunks.

Change-Id: I5e8867077ed2908b7f9c5d8bde34d0401f7fe446
Reviewed-on: https://chromium-review.googlesource.com/c/1385164
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58484}