Reopen the bug.

This test case is under zktest/test2/B50-3210336-2.zul

<zk>
Maximize the panels respectively. If the panel does not occupy the whole area, it is a bug.
<portallayout maximizedMode="whole" style="border:2px solid red" height="500px">
<portalchildren style="padding:5px;border:2px solid gray">
<panel title="Panel 1" border="normal" maximizable="true" vflex="1">
<panelchildren>1/2 ABCD</panelchildren>
</panel>
<panel title="Panel 2" border="normal" maximizable="true" vflex="1">
<panelchildren>1/2 EFGH</panelchildren>
</panel>
</portalchildren>
</portallayout>
</zk>