title: Ext.getCmp is not working in ExtJS4
body: <p>I am trying to create a component and access it inside controller. But while accessing the component by id, it is not returning the component. It always returns undefined. Please find below the code.</p>
  
  <p>enter code here</p>
  
  <pre><code>//Component creation in view layer as below
  
  Ext.define('MyApp.view.performance.grid.IFrameGridCmp', {
      extend: 'Ext.panel.Panel',
      alias: 'widget.crMainPanel',
      id:'mainPanelId',
      layout: {
          align: 'stretch',
          type: 'vbox'
      },
      border:0,
      resizable: false,
      forceFit: true,
      autoWidth: true,
      initComponent: function() {
          Ext.apply(this, {
              items: [
                  {
                      xtype:'panel',
                      flex:.02,
                      border:0
                  },
                  {
                      xtype:'crHeaderPanel',
                      flex:.05
                  },
                  {
                      xtype: 'crUpperPanel',
                      flex: 0.93
                  },
                  Ext.create('Ext.Component', {
                      autoEl: {
                          tag: 'iframe', 
                          cls: 'x-hidden', 
                          src: Ext.SSL_SECURE_URL
                      },
                      id:'FileDownloader',
                      height:0,
                      listeners: {
                          afterrender: function () {
                              this.getEl().on('load', function () {
                                  console.log('loaded download frame');
                              });
                          }
                      },
                      load: function(config){
                          var e = this.getEl();
                          e.dom.src = config.url + (config.params ? '?' + Ext.urlEncode(config.params) : '');
                          e.dom.onload = function() {
                              Ext.getBody().unmask();
                              if(e.dom.contentDocument.body.childNodes[0].wholeText == '404') {
                                  Ext.Msg.show({
                                      title: 'Attachment missing',
                                      msg: 'The document you are after can not be found on the server.',
                                      buttons: Ext.Msg.OK,
                                      icon: Ext.MessageBox.ERROR 
                                  });
                              }
                          };
                      }
                  })
              ]
          });
          this.callParent(arguments);
      }
  });
  
  ========================================
  
      enter code here
  
  //Accessing the controller as below in controller
  
  views: ['performance.grid.IFrameGridCmp'],
  
  //The below line gives error
  var downloader = Ext.getCmp('FileDownloader');
              downloader.load({
                  url: '/APXUI/data/json/xls?exportData='+Ext.JSON.encode(records)
              });
  </code></pre>