[9] Code Review Request For 8155998: Encapsulate JavaFX impl_* implementation methods in stage package

[Chien Yang]

Hi Jonathan and Kevin,

Please review the proposed fix:

JIRA: https://bugs.openjdk.java.net/browse/JDK-8155998
Webrev: http://cr.openjdk.java.net/~ckyang/JDK-8155998/webrev.00/

Thanks,
- Chien