Steps to reproduce:

1. Launch gtk3-demo
2. Launch the Tree Store demo
3. Examine the checkboxes using Accerciser's Interface Viewer

Expected results: The Action interface would include 'toggle'.
Actual results: The Action interface lacks 'toggle'.

Notes:

* This action used to be present. I do not yet know when it went away.

* Primary impact: Orca cannot present the fact that a cell can be checked.

* Secondary impact: Due to the lack of STATE_CHECKABLE, Orca relies upon this action as a means to identify which toggle-able table cells can be checked. If an object can be checked, it THEN checks for STATE_CHECKED. Thus at the moment, Orca is not presenting "checked" or "unchecked" for these items. The best it can do is always look for STATE_CHECKED and present it if it is found; but that would be a work around, and it still would not solve the problem for items which are unchecked.