Reason for revert:
Speculative revert to see impact on crbug.com/659531
Original issue's description:
> [heap] Add a guard for restarting the memory reducer after mark-compact.
>
> Currently it is possible to get into a cycle of
> mark-compact -> memory reducer -> mark-compact -> memory reducer ...
> where the memory reducer does not free memory.
>
> This patch ensures that the memory reducer restarts only if the
> committed memory increased by sufficient amount after the last run.
>
> BUG=
TBR=hpayer@chromium.org,davidroutier17@gmail.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=
Review-Url: https://codereview.chromium.org/2472053003
Cr-Commit-Position: refs/heads/master@{#40737}
3c96c5e232