Currently the new space linear allocation area boundaries are fetched
with sequentially consistent atomic loads.

This can be replaced with an acquire load.

Change-Id: Ib08e0bc0ae0ce79fee3723d29dc9a99a5d771880
Reviewed-on: https://chromium-review.googlesource.com/c/1326467Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57381}