GTKLookAndFeel throws UnsupportedLookAndFeelException in headless environment, so adding `headful` keyword to the test.
Alternatively, we can catch `UnsupportedLookAndFeelException` and ignore the LaF. --------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - 8393249: JOptionPaneInternalFrameNotClosableTest fails in headless mode with unsupported GTK LookAndFeel Changes: https://git.openjdk.org/jdk/pull/33139/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=33139&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8393249 Stats: 2 lines in 1 file changed: 1 ins; 1 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/33139.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/33139/head:pull/33139 PR: https://git.openjdk.org/jdk/pull/33139
