Code Review Request For RT-39873: [Mac] Enable parallel execution of FX thread and Renderer thread for JFXPanel, FXCanvas

[Chien Yang]

Hi Kevin,

Please review the simple proposed fix:

JIRA: https://javafx-jira.kenai.com/browse/RT-39873
Webrev: http://cr.openjdk.java.net/~ckyang/RT-39873/webrev.00/

- Chien