The current V8HugeMaxOldGenerationSize feature increases the JS heap size for
systems with larger than 16 GB physical memory. This cl adds support for 16 GB
configuration.

Because a small portion of memory is reserved by hardware, the physical memory
calculation here is rounded up to GB so the actual installed memory is checked.

Bug:chromium:958974

Change-Id: Idaf2e03a43ba6c3c40bb771296d06b87032c2725
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1734038
Commit-Queue: Maggie Chen <magchen@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63104}