[8u20] Review request for RT-35025: Scene turns black sometimes.

[Vadim Pakhnushev]

Chien, Kevin,
Please review a fix for this:
http://cr.openjdk.java.net/~vadim/RT-35025/webrev.00/ 
<http://cr.openjdk.java.net/%7Evadim/RT-35025/webrev.00/>
https://javafx-jira.kenai.com/browse/RT-35025