This is a reland of 9072bef0

Original change's description:
> Reland "[heap] Added per-page array buffer accouting (external memory)."
> 
> This is a reland of d4792e8f
> 
> Original change's description:
> > [heap] Added per-page array buffer accouting (external memory).
> > 
> > Bug: chromium:845409
> > Change-Id: Ibc568cdc501edf5d84d9c6379aff58be069369af
> > Reviewed-on: https://chromium-review.googlesource.com/1114602
> > Commit-Queue: Rodrigo Bruno <rfbpb@google.com>
> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#54028}
> 
> Bug: chromium:845409
> Change-Id: I6b11d7f66313bcbcc31be9217c1b780cf3eaee99
> Reviewed-on: https://chromium-review.googlesource.com/1116638
> Commit-Queue: Rodrigo Bruno <rfbpb@google.com>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54066}

Bug: chromium:845409
Change-Id: Icff4e2a2b974942f73f5e6bb0bfd6ee8655e8ce7
Reviewed-on: https://chromium-review.googlesource.com/1119985Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Rodrigo Bruno <rfbpb@google.com>
Cr-Commit-Position: refs/heads/master@{#54108}