Makes it clearer what this does. Added comments to explain it.

Change-Id: I90b0686f8a607cea32c482591b924e9103f7f445
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2205693
Commit-Queue: Simon Zünd <szuend@chromium.org>
Auto-Submit: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67846}