With bug 1694820 complete, and bug 1713130 in progress, my next step is to convert the whole
#view-box to html. This would include changing the custom elements to html.
I might also change the class hierarchies (e.g. I don't think it makes sense that
MozCalendarEventBox inherit from
MozCalendarEditableItem), and this is probably a good opportunity to do some general code clean up as well.
I'll be keeping an eye on the accessibility tree as well.