[8u] Review request: RT-36551: [Media] Mac: Crash in media disposer thread

[anton nashatyrev]

Hello,

    could you please review the following fix:

Webrev: http://cr.openjdk.java.net/%7Eanashaty/RT-36551/8/webrev.00/
Issue: https://javafx-jira.kenai.com/browse/RT-36551

Thank you!
Anton.