This change may slow down deserialization of the snapshot but may result in less fragmentation.

Bug: v8:7887
Change-Id: Id8bb9f1a561b08b7ae0f10b80aa77bc00eb23172
Reviewed-on: https://chromium-review.googlesource.com/1125722Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54198}