title: ExtJs adding items after viewport is created
body: <p>I would like to check with you guys. Are these two blocks of codes doing the same thing?</p>
  
  <pre><code>me.viewport = new Ext.container.Viewport({
      items: [ me.mainPanel]
  });
  </code></pre>
  
  <p>and</p>
  
  <pre><code>Ext.application({
      autoCreateViewport: true,
  //then later ....
  viewport = Ext.getCmp('viewport');
  viewport.Add(me.mainPanel);
  </code></pre>
  
  <p>Except that one is created at the very beginning, other one is created on the spot. But they do the same job other than that, right? Thank you :)</p>