<Swing Dev> RFR JDK-8251187: Mark BasicComboNPE regression test as headful

[Prasanta Sadhukhan]

Hi All,

Please review a test-fix for an issue seen failing in mach5 due to test 
throwing HeadlessException.

Test needs to be marked as headful and also setPopupVisible(false) is 
used as setPopupVisible(true) gives StackOverflowError in macOS, which 
will be investigated separately.

setPopupVisible(false) also can be used to test 6709913 fix. mach5 job 
link in JBS.

diff -r 964a2a2c403b 
test/jdk/javax/swing/plaf/basic/BasicComboBoxUI/BasicComboNPE.java
--- a/test/jdk/javax/swing/plaf/basic/BasicComboBoxUI/BasicComboNPE.java 
Wed Aug 05 17:49:11 2020 +0530
+++ b/test/jdk/javax/swing/plaf/basic/BasicComboBoxUI/BasicComboNPE.java 
Wed Aug 05 20:59:20 2020 +0530
@@ -22,6 +22,7 @@
   */

  /* @test
+   @key headful
     @bug 6709913
     @summary Verifies BasicComboBoxUI.isPopupVisible does not return NPE
     @run main BasicComboNPE
@@ -52,7 +53,7 @@
      @Override
      public ComboBoxModel getModel()
      {
-        setPopupVisible(true);
+        setPopupVisible(false);
          isPopupVisible();
          return super.getModel();

      }
Regards
Prasanta