While testing the fix for JDK-8202990, I got intermittent crashes in the newly added unit test. See the discussion in the PR https://github.com/openjdk/jfx/pull/279 . This appears to be caused by the WebPageShim::paint method in the test framework, which calls WebPage::paint to perform rendering of a web page for the purpose of testing the results. That shim method, which was added in support of the unit test for JDK-8215702, is called on the JavaFX application thread. However, the WebPage::paint method must be called only on the Rendering Thread.