title: Flex, filter tree using ITreeDataDescriptor without reload and close all nodes
body: <p>working with flex 4 and implementing filtering using ITreeDataDescriptor.
  Filtering worked as expected like the following code snippet </p>
  
  <p>however, i am trying to create a on-demand type of filter where user would type in the search clause in a TextInput, and as the user types, the tree nodes would be filtered on the fly.</p>
  
  <p>my implementation now is have user click on the search button and then reapply the dataDescriptor then reload the data. A big problem is that the whole tree collapses after setting the dataProvider again.</p>
  
  <p>any suggestion on how the on-demand filter can be achieved?</p>
  
  <pre><code>var dataFilter:ServicePricingFilter = new MyFilter();
  dataFilter.searchString = this.txtSearchKeyword.text;
  this.treeService.dataDescriptor = new MyDataDescriptor(dataFilter);
  this.treeService.dataProvider = getTreeData();
  </code></pre>