We did not merge Percona XtraDB 5.6.40-84.0 yet.
The changes in it are mostly cosmetic, except for
2 bug fixes from Oracle MySQL 5.6.40, which could
be security bugs.

This was achieved by taking the applicable parts
of an earlier InnoDB commit to XtraDB:

git diff 15ec8c2f{~,} storage/innobase|
sed -e s+/innobase/+/xtradb/+|patch -p1