Make ChangeRow work with new ORMTable.

This is in preparation for core change I86368821.

Note that this change makes ChangeRow work with the
old and new version of ORMTable, so it can and should be
merged before the core change.

Change-Id: I98a67ae7e5473528399954d2750ba82539826e9d
Merge "Make ChangeRow work with new ORMTable." into mw1.21-wmf12b