Review Request: JDK-8200587: Fix mistakes in FX API docs

[Nir Lisker]

Hi Kevin,

After JDK-8200749 is committed, please review the fixes for documentation
mistakes:

https://bugs.openjdk.java.net/browse/JDK-8200587
http://cr.openjdk.java.net/~nlisker/8200587/webrev.00/

Thanks,
Nir