Encapsulates special reservation / allocation behavior for builtin
deserialization.

Bug: v8:6624
Change-Id: Ic784ed43b607c881b356c6e535c9dbe185e1d4cd
Reviewed-on: https://chromium-review.googlesource.com/716229
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48638}