When passing an instance of a non-public nested class to use via javascript in a WebView to call back into Java, the JVM crashes hard (native stack overflow) when the method on that object is called from the javascript.

Under Java 8b109 this merely results in an exception:
Exception in thread "JavaFX Application Thread" java.lang.IllegalAccessException: Class sun.reflect.misc.Trampoline can not access a member of class webviewcallback.WebViewCallback$JavaAccessObject with modifiers "public"