We need a Toolkit shutdown hook that can be used by other parts of the system (e.g., media) to clean up resources, etc. Something like:

public void Toolkit.addShutdownHook(TKShutdownHook hook);
public void Toolkit.removeShutdownHook(TKShutdownHook hook);

These shutdown hooks would be called by Toolkit.exit() on the JavaFX application thread and could be used to dispose of resources.