This occurs in AWT PIT build for mustang b49 on all platforms.

Desktop.isDesktopSupported method throws ClassCastException in headless mode.

java.lang.ClassCastException: sun.awt.HeadlessToolkit cannot be cast to sun.awt.SunToolkit
        at java.awt.Desktop.isDesktopSupported(Desktop.java:149)

To reproduce:
Run the attached testcase passing the command line option: -Djava.awt.headless=true