title: Ext.Defer gives getAsynchronousLoad Error
body: <p>I've just defined a combobox. Firstly it loads a <code>country</code>list and when select a value it's fire a <code>change</code> event which doing a <code>ajax</code> query to DB within searching service;</p>
  
  <p>The thing; this configuration works pretty well when I click and open combobox items. But when I'm typing to combobox's field it's fires listener's <code>store.load</code> and because of none of country selected yet, the search query url gives not found errors of course.</p>
  
  <pre><code>{
                      xtype: 'countrycombo',
                      itemId: 'countryName',
                      name:'country',
                      afterLabelTextTpl: MyApp.Globals.required,
                      allowBlank: false,
                      flex: 1,
                      // forceSelection: false,
                      // typeAhead: true,
                      // typeAheadDelay: 50,
                      store: {
                          proxy: {
                              type: 'ajax',
                              // isSynchronous: true,
                              url: MyApp.Globals.getUrl() + '/country/list?limit=250',
                              // timeout: 300000,
                              reader: {
                                  type: 'json',
                                  rootProperty: 'data'
                              }
                          },
                          pageSize: 0,
                          sorters: 'description',
                          autoLoad: true
                      }
                      ,
                      listeners: {
                          change: function (combo, countryId) {
                              var cityStore = Ext.getStore('cityCombo');
                              cityStore.getProxy()
                                  .setUrl(MyAppp.Globals.getUrl() + '/city/view/search?query=countryid:'+ countryId);
                              // Ext.defer(cityStore.load, 100);
                              cityStore.load();
                          }
                      }
                  },
  </code></pre>
  
  <p>I've tried several things as you see in code above to set a delay/timeout for <strong>load</strong> during typing to combobox text field; <code>Ext.defer</code>, <code>timeout</code>config on proxy, <code>typeAhead</code> config on combo but none of them worked! </p>
  
  <p>I thought that <code>Ext.defer</code> is the best solution but it gives this error:</p>
  
  <p><code>Uncaught TypeError: me.getAsynchronousLoad is not a function at load (ProxyStore.js?_dc=15169)</code></p>
  
  <p>How can I set a delay/timeout to combobox to fires <code>load</code> function?</p>