... like AllocatePage[s](), FreePages() and SetPermissions().
This CL also changes base::PageAllocator to cache AllocatePageSize and CommitPageSize
values returned by the OS.
This is a necessary cleanup before introducing BoundedPageAllocator.

Bug: v8:8096
Change-Id: Ifb7cdd2caa6a1b029ce0fca6545c61df9d281be2
Reviewed-on: https://chromium-review.googlesource.com/1209343Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55690}