<Swing Dev> [9] Review request for 8074883: Tab key should move to focused button in a button group

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:

bug: https://bugs.openjdk.java.net/browse/JDK-8074883

webrev: http://cr.openjdk.java.net/~ssadetsky/8074883/webrev.00/

To avoid unexpected selection change the selected button of a button 
group should always grab focus when focus is transferred form component 
outside the group to any unselected button inside the group in case of 
traversal or initial container activation actions.

--Semyon