[8u Review Request] RT-37551: loading user-agent stylesheets one at a time from PlatformImpl is inefficient

[David Grieve]

Steve, Kevin -

I'd like for you to review these changes as they affect PlatformImpl.
https://javafx-jira.kenai.com/browse/RT-37551
http://cr.openjdk.java.net/~dgrieve/RT-37551/webrev.00/ 
<http://cr.openjdk.java.net/%7Edgrieve/RT-37551/webrev.00/>