I've derped on this for far too long and have no idea right now.
Just fucked around with this more and I still haven't found a way to make it work. Closing out as a browser bug and documenting it in the browser bugs page.
For those following along at home, here's a JS Bin that attempted a fix with wrapping the buttons in an extra element that provides the equivalent of a tr. That didn't work either. Only thing that did was the extra wrapper.
Document #12476 bug in the wall of bugs