[REVIEW REQUEST] onShowing, onHiding, etc events in ComboBox

[Jonathan Giles]

Hi all,

Another review request: http://javafx-jira.kenai.com/browse/RT-20855

This request basically asks to add callbacks into ComboBox related to 
the popup ListView showing, being shown, hiding, and being hidden. This 
API is the same as in Menu and other places. In other words, there is 
now onShowing, onShown, onHiding and onHidden callbacks you may listen to.

There is a patch attached to the Jira issue for your perusal.

Thanks,
Jonathan