Add comments and simpify code a bit for less chance of cargo culting.

Change-Id: Ica3fc60b0b7c11cc99a4c9ba9e3255662bbbb6bc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2642459
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72472}