title: DockedItems not displayed in preview
body: <p>Any idea why the docked items not displayed in the preview? Here is the code.</p>
  
  <pre><code>Ext.setup({
      onReady:function(){
          var top_toolbar= [{
              xtype:'toolbar',
              ui:'dark',
              dock:'top',
              title:'Login Form'
          }]
          var loginForm = new Ext.form.FormPanel({
              items:[{
                  xtype:'fieldset',
                  items:[{
                      xtype:'textfield',
                      label:'Username',
                      name:'u_name',
                      labelWidth:100
                  },{
                      xtype:'passwordfield',
                      label:'Password',
                      name:'u_password',
                      labelWidth:100
                  }]
              }]
          });
          var formPanel=new Ext.Panel({
              fullscreen:'true',
              layout:'fit',
              dockedItems:top_toolbar,
              items:[loginForm]
          });
      }
  });
  </code></pre>
  
  <p>I am just trying to create a login page, with the textfields for username and password and need to include the toolbar docked on top which has the title 'Login Form'. In the preview i get the textfields with label but it does not show the toolbar. am I doing anything wrong with the code?</p>
  
  <p>Any help would be appreciated. Thanks in advance.</p>