This is a prepratory change to allow more refactoring of code between
New and PagedSpace.

Bug: 
Change-Id: Iabda8365cae0de2278d772e56728e900e688c9aa
Reviewed-on: https://chromium-review.googlesource.com/815904Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ali Ijaz Sheikh <ofrobots@google.com>
Cr-Commit-Position: refs/heads/master@{#49966}