Review request: RT-34586,Gtk: MenuButton in MenuButton context on Linux doesn't work

[Martin Sladecek]

Anthony, Alexander,

please review the following:

JIRA: https://javafx-jira.kenai.com/browse/RT-34586
Webrev: http://cr.openjdk.java.net/~msladecek/rt-34586/webrev.00/

Thanks,
-Martin