<Swing Dev> [10] Review Request: 8196196 Headful tests should not be run in headless mode

[Sergey Bylokhov]

Hello.
Please review small test cleanup for jdk11.

  - "@key headful" was added to some tests which requires 
DISPLAY/xorg/gtk/gnome etc.
  - Some swing tests were updated to skip unsupported look and feels, 
for example GTK LookAndFeel can be installed(bundled) but is not 
necessary supported.

The final goal of this and some other future fixes is to run all 
non-headfull tests in parallel and speedup the tests execution.

Bug: https://bugs.openjdk.java.net/browse/JDK-8196196
Webrev can be found at: http://cr.openjdk.java.net/~serb/8196196/webrev.02/


-- 
Best regards, Sergey.