relate to http://tracker.zkoss.org/browse/ZK-1589

zul code

<zk xmlns:n="native">
<button id="btn" label="Invalidate" onClick="cave.invalidate()">
</button>
<div id="cave">
<n:div>
<window title="Root" border="normal">
<n:div>
<window title="Nest inside native" border="normal">
</window>
</n:div>
</window>
</n:div>
</div>
</zk>