#1634 transitionend event should fire on CSS transitions

[Jake Cobb]

Elements with a CSS transition should fire the transitionend (MDN page) event when the transition is done. In Chrome mode, you might also fire webkitTransitionEnd.

Currently, this event never fires. If CSS transitions are not implemented (I can't see that they are), I think it would be best to fire the event right away when the style changes the position/size.

Test case patch attached.