innodb_ibuf_active_contract shows up in 5.5.22 even though the changelog says it was renamed to innodb_ibuf_active_merge

The doc says it should be innodb_ibuf_active_merge:

http://www.percona.com/doc/percona-server/5.5/scalability/innodb_insert_buffer.html

and that it defaults to '0'. However, I have this server:

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Server version: 5.5.22-55 Percona Server (GPL), Release rel25.2, Revision 237

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mysql> show variables like 'innodb_ibuf%';
+-----------------------------+-------------+
| Variable_name | Value |
+-----------------------------+-------------+
| innodb_ibuf_accel_rate | 100 |
| innodb_ibuf_active_contract | 1 |
| innodb_ibuf_max_size | 53687009280 |
+-----------------------------+-------------+
3 rows in set (0.00 sec)

where it is named innodb_ibuf_active_contract and apparently defaulting to 1.

The changelog is the only place I could find mention of innodb_ibuf_active_contract:

http://www.percona.com/doc/percona-server/5.5/release-notes/Percona-Server-5.5.8-20.0.html