[9] Review request for 8157065: There is no the focus border on the selected tab.

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:
bug: https://bugs.openjdk.java.net/browse/JDK-8157065

webrev: http://cr.openjdk.java.net/~ssadetsky/8157065/webrev.00/

GTK LnF draws focus only when a default tab header is used. If custom 
tab renderer is installed the input focus is not shown.
The fix implements the omitted scenario.

--Semyon