Use of "importClass" or "importPackage" function in Javascript within BXML files won't work under Java 8 Nashorn script engine

A small script such as this in a BXML file now will not work in Java 8:
<bxml:script>
importClass(org.apache.pivot.wtk.Button);
function isSelected(state)

{ return state == Button.State.SELECTED; }

</bxml:script>
The reason is that the "importClass" function is not present in the base Nashorn engine, but is provided by a compatibility library: "mozilla_compat.js".