This is a reland of 34e3e7f9
Original change's description:
> Introduce gc flag for fuzzing over compaction.
> 
> Bug: v8:6972
> Change-Id: If1f4ee04ae00c6ae1e037bbb1ca758e952a8f843
> Reviewed-on: https://chromium-review.googlesource.com/738112
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Commit-Queue: Michał Majewski <majeski@google.com>
> Cr-Commit-Position: refs/heads/master@{#49191}

Bug: v8:6972
Change-Id: I690a72a6d5da17c6f15449b2be4cbb681a67e60e
Reviewed-on: https://chromium-review.googlesource.com/756894Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michał Majewski <majeski@google.com>
Cr-Commit-Position: refs/heads/master@{#49195}