Heap::InNewSpace only needs to access the heap for a DCHECK and the part
that uses the heap only needs it if the object is in NEW_SPACE, in which
case getting it via pointer magic is fine.

Bug: v8:7786
Change-Id: Iaac237a3b8bcc9d55e436e3f972475e04b97f1f8
Reviewed-on: https://chromium-review.googlesource.com/1127798
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54345}