The size is now computed as a fraction of the old space size:
- for low memory devices (<512MB) the fraction is 1 / 256.
- for all other devices the fraction is 1 / 128.

The values were chosen to minimize the difference between the new
and the old heuristics.

Bug: v8:9306

Change-Id: I3246fe2d6fc589af6220e2566e3f10fb13470b82
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1632158Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61947}