title: Extjs child item not filling the parent container
body: <p>My problem is, even if I used "layout: 'fit'" in all my children items within a boarder layout, they just shrinks into a small box rather than fill the parent, as described in fit layout.</p>
  
  <p>I want the EDS.view.selector.Container to fill the "navigation" section of my boarder layout.</p>
  
  <pre><code>(Code excerpt)
  
  Ext.define('EDS.view.selector.Container', {
      extend: 'Ext.panel.Panel',
      alias : 'widget.selectorcontainer',
  
      layout: 'fit',
      initComponent: function(){
           this.items = [
                  {
                      xtype: 'tabpanel',
                      defaults: {
                          bodyPadding: 10
                      },
                      layout: 'fit',
                      items:[
                           {
                               title: 'Organization',
                               id: 'selector-organization',
                               tag: 'div',                             
                               html: 'div here',
                               height: '100%',
                           }                  
                      ]
                  }
          ],
          this.callParent();
      },
  });
  
  
  
  (Controller)
  init: function(){
      console.log('controller.init()');
  
      new Ext.Viewport({
          title: 'Data Analysis',
          layout: 'border',
          defaults: {
                  collapsible: true,
                  split: true,
                  bodyStyle: 'padding: 15px',
          },
          items: [{
              title: 'Navigation',
              region:'west',
              margins: '5 0 0 0',
              cmargins: '5 5 0 0',
              width: 600,
              minSize: 100,
              maxSize: 250,
                  items: [
                      {
                      id: 'selector-container',
                          xtype: 'selectorcontainer',
                          layout: 'fit',
                      }
              ]
          },{
              title: 'Main Content',
              collapsible: false,
              region:'center',
              margins: '5 0 0 0'
          }]
      });
  }
  </code></pre>