We need to keep the new space mark bits as they are still required for
pointer updating.

TBR=hpayer@chromium.org
NOTRY=true

Bug: chromium:651354
Change-Id: Idc85f08a3b6525dd1ca932585f5e696a22b12808
Reviewed-on: https://chromium-review.googlesource.com/522609Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45690}