Reland of [heap] Simplify distribution of remaining memory during sweeping & compaction (patchset #1 id:1 of https://codereview.chromium.org/1661723003/ )

Reason for revert:
Bisection results show that this was not the culprit.

Original issue's description:
> Revert of [heap] Simplify distribution of remaining memory during sweeping & compaction (patchset #2 id:80001 of https://codereview.chromium.org/1653973003/ )
>
> Reason for revert:
> Very likely blocking roll: https://codereview.chromium.org/1652413003/
>
> Original issue's description:
> > [heap] Simplify distribution of remaining memory during sweeping & compaction
> >
> > BUG=chromium:524425
> > LOG=N
> >
> > Committed: https://crrev.com/f72923526ccaa8faef5c977267b0c074c4a44dfa
> > Cr-Commit-Position: refs/heads/master@{#33668}
>
> TBR=hpayer@chromium.org,mlippautz@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=chromium:524425
>
> Committed: https://crrev.com/a9441b0e7a2a56c2047482a3cc66e3ca2255444b
> Cr-Commit-Position: refs/heads/master@{#33695}

TBR=hpayer@chromium.org,mlippautz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:524425

Review URL: https://codereview.chromium.org/1663013002

Cr-Commit-Position: refs/heads/master@{#33696}