Calls to madvise(MADV_FREE_REUSABLE) [when discarding/decommitting memory]
should be paired with calls to madvise(MADV_FREE_REUSE) [when reusing/committing
memory]. The latter is purely for accounting purposes.

Bug: chromium:823915
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: Ib1758fd72c5ad4dfe731f5d9a6dbaf75b1e0e14b
Reviewed-on: https://chromium-review.googlesource.com/988193
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52674}