This is in contrast to not dispatching the event altogether in `Flex` when
the event is not contained in the flex element bounds. That approach was
problematic because it didn't give an opportunity to `MouseEventHandler`s
to handle mouse move events when they didn't intersect with the element bounds,
causing elements to never clear their hover state, cursor style, etc.
Nathan SoboandAntonio Scandurra
Max Brunsfeld