Right, there is a patch series here: https://github.com/timhunt/moodle/compare/master...MDL-26425
The two changes I actually need for
MDL-20636 are https://github.com/timhunt/moodle/commit/d5af1a5c089d63780dd9b07ba98b64903970107a and https://github.com/timhunt/moodle/commit/a17cc49fba7ce526805bfce65358dae3c7c4f7eb. The rest of the cleaning up I did to try to be helpful, and because I hate ugly code.
There is only one other change in functionality in these patches. Well, it is not really a change, but I stripped out some old code that has not worked for ages. See https://github.com/timhunt/moodle/commit/42606aaa3143255623a3874a128cb7e8599f90e8.
Apart from that, functionality should not have changed.
To test this properly, we really need to test all the places this class is used. My searching finds this complete list:
In practice, I think we only need to test a reasonable sample of the tables on these pages. You need to test sorting, collapsing columns, paging, and restricting the list of users by initial, and so on.