<Swing Dev> [9] Review request for 8152968: JTree Collapse Buttons Clipped Off Under GTK

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:

bug: https://bugs.openjdk.java.net/browse/JDK-8152968

webrev: http://cr.openjdk.java.net/~ssadetsky/8152968/webrev.00/

GTK lib paints the expander icon bigger then the dimension returned by 
the "expander-size" property.

The fix increases the allocated space by adding insets of size 2 to make 
the tree component UI looks as in native GTK apps.

Also a GTK3 issue is fixed: the tree expander state was not changed from 
collapsed to expanded.

Test would require native application so the issue is noreg-hard.

--Semyon