Code Review Request For RT-39783: Move Mac specific implementation (support CALayer) out of platform independent code path

[Chien Yang]

Hi Kevin,

Please review this simple change.

JIRA: https://javafx-jira.kenai.com/browse/RT-39783
Webrev: http://cr.openjdk.java.net/~ckyang/RT-39783/webrev.00/

Thanks,
- Chien