spun off bug 503727 comment #37. nsITreeView methods like setCellValue or cycleCell are required to call invalidation methods of tree box object which is handled by accessibility module to fire accessibility events. However, for example, when user clicks on checkbox cell then tree view is redrawn even if setCellValue doesn't invalidate the cell. It leads to sighted users see up to dated tree view but blind users because AT softwares don't get proper accessibility events.

Moving to Core:XUL per https://bugzilla.mozilla.org/show_bug.cgi?id=1455336