Update the run command on test file to "@run testng/othervm -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel InternalFrameDemoTest"

Attached changed file - InternalFrameDemoTest.java

java version "12-ea" 2019-03-19
Java(TM) SE Runtime Environment 19.3 (build 12-ea+6)
Java HotSpot(TM) 64-Bit Server VM 19.3 (build 12-ea+6, mixed mode)

Command: ./swingsanity/jtreg/bin/jtreg -verbose:all -jdk:./swingsanity/testjdk/jdk-12 -dir:./swingsanity/testbase/12/test/jdk sanity/client/SwingSet/src/InternalFrameDemoTest.java

Attached full logs - InternalFrameDemoTest.jtr

Reproducible: Always