title: how to mask one of the ContentPanels in AccordionLayoutContainer
body: <p>There is a accordionLayoutContainer in my project,and i want to mask one of the contentpanels,i use this code:</p>
  
  <pre><code>ContentPanel cp1 = new ContentPanel(appearance);
  cp1.mask("message");
  </code></pre>
  
  <p>but the whole accordionLayoutContainer was mask,not the cp1.
  thanks for suggestions!</p>