title: Extjs setRootNode() on TreeGrid isn't loading children of the object
body: <p>I am currently building a project using Ext JS 4.2 this is the first time I am using TreeGrids and TreeStores so it is very possible I am misunderstanding the structure somewhere. Currently the issue seems to be when I use setRootNode(JSON) it refreshes the tree but it only displays the root node and none of its children. Here is what it currently creates.</p>
  
  <p>Using the developer tools in chrome this is what the object looks like before it is passed in.</p>
  
  <pre><code>Object {text: ".", Item Number: "P00001", original: "P00001", children: Array[2]}
  </code></pre>
  
  <p>Once it is passed in using setRootNode(Object) it only displays the root. However I have noticed that looking at the grid.tree.root property all the data is in there which makes me wonder why it is not being loaded into the treegrid.</p>
  
  <p>Here is a snippet of my code that loads the necessary data. var grid refers to the tree panel component. store.load causes a jsp call that loads in meta data that dynamically creates the columns / fields for the treegrid and model which is functioning correctly.</p>
  
  <pre><code>onPanelAfterRender: function(){
      var grid = Ext.getCmp('BOMGrid');
      var store = Ext.getStore('BOMGridStore');
      store.load();
      //var me = Ext.getCmp('main-page');
      grid.setLoading('Loading BOM...');
      Ext.Ajax.request({
          url : 'loadbom.jsp',    
          timeout: 300000,
          params : {
          },
          success: function (response, opt) {
              grid.setLoading(false);
              var res = Ext.JSON.decode(response.responseText);
              if (res.success) {  
                  console.debug(res.results[0]);
                  grid.setRootNode(res.results[0]);
              }
              else {
                      console.debug("JSON failure");
                      Ext.Msg.alert('Error', 'Invalid part number');
              }
  
          },
          failure: function(response,options){
              console.debug("major failure");
              grid.setLoading(false);
              Ext.Msg.alert('Error', 'Connection failed&lt;br&gt;' + response.responseText);
              }
          });
  }
  </code></pre>
  
  <p>If you need additional information or for me to clarify something please ask me I would appreciate any help that I could possibly get.</p>