[8] Request for review: JDK-8020927 JLightweightFrame API should export layout properties change notifications

[Anton V. Tarasov]

Please, review a fix.

jira: https://jbs.oracle.com/bugs/browse/JDK-8020927
webrev: http://cr.openjdk.java.net/~ant/JDK-8020927/webrev.0
Layout bounds notifications are added to internal JLightweightFrame API.

(Just FYI, related fx changes are here: 
http://cr.openjdk.java.net/~ant/RT-30650/webrev.0)

Thanks,
Anton.