- Changes d8 ArrayBuffer::Allocators to restrict size to < 2GB on the
  Allocate/AllocateUninitialized paths. Reserve can still create larger
  ArrayBuffers.

Bug: chromium:793196
Change-Id: I662f8c681f715457d630df31039a1ea4d17cfafc
Reviewed-on: https://chromium-review.googlesource.com/817763
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49973}