<Swing Dev> [9] Review request for 8146301: Enter key does not work in a deserialized JFileChooser

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:

bug: https://bugs.openjdk.java.net/browse/JDK-8146301
webrev: http://cr.openjdk.java.net/~ssadetsky/8146301/webrev.00/

This is a regression of JDK-8021253 in which explicit setting the 
default button was moved to the hierarchy listener but this listener 
disappears after serialization/deserialization cycle because it is not 
serializable. The solution is to make it serializable.

--Semyon