title: Intercepting GWT RequestFactory requests
body: <p>Is there a way to intercept RequestFactory requests on client side?</p>
  
  <p>I want to intercept calls like this:</p>
  
  <pre><code>dummyRequest.dummyOperation().fire( new Receiver&lt;String&gt;() {
    @Override
    public void onSuccess(String response) {        
    }
  });
  </code></pre>
  
  <p>The idea is to show some loading indication when communicating with server.</p>