JDK-8152395: Fix toolbar overflow control

[Diego Cirujano]

Hi,

I'd like to request a review for JDK-8152395 available as a PR on

Github: *https://github.com/javafxports/openjdk-jfx/pull/318
<https://github.com/javafxports/openjdk-jfx/pull/318>*

JBS: *https://bugs.openjdk.java.net/browse/JDK-8152395
<https://bugs.openjdk.java.net/browse/JDK-8152395>*

Thanks.

Diego