title: Seeming to set a 1-directional databind even though it should be bidirectional
body: <p>Been working with 2 files:  <em>my_ajax_fetcher.data/html</em> with the data as follows:</p>
  
  <p><em>my_ajax_fetcher.dart</em></p>
  
  <pre><code>@HtmlImport('my_ajax_fetcher.html')
  library webserver_ajax.lib.iron_ajax;
  
  import 'package:web_components/web_components.dart';
  import 'package:polymer/polymer.dart';
  import 'package:polymer_elements/iron_ajax.dart';
  import 'package:polymer_elements/iron_request.dart';
  
  ///Uses [IronAjax]
  @PolymerRegister('my-ajax-fetcher')
  class IronAjaxSample extends PolymerElement {
  
    @property
    String f_name;
  
    @property
    String l_name;
  
    @property
    int identification;
  
  
    //IronAjax ia = querySelector('myAjaxId');
  
    IronAjaxSample.created() : super.created(){
      print("created.");
      //ia.generateRequest();
    }
  
  
    @reflectable
    void handleResponse ( [CustomEventWrapper cew, IronRequest ir] ){
      print("handle response fired");
      var data = ir.response;
      f_name = data["f_name"];
      l_name = data["l_name"];
      identification = data["id"];
  
      print("$f_name $l_name: $identification");
    }
  }
  </code></pre>
  
  <p><em>my_ajax_fetcher.html</em></p>
  
  <pre><code>&lt;dom-module id="my-ajax-fetcher"&gt;
      &lt;template&gt;
  
          &lt;iron-ajax id="myAjaxId" auto
            url="http://localhost:8675/test_server/v1/users/35"
            handle-as="json"
            on-response="handleResponse" &gt;&lt;/iron-ajax&gt;
  
          &lt;div&gt;First Name: {{f_name}}&lt;/div&gt;
          &lt;div&gt;Last Name:  {{l_name}}&lt;/div&gt;
          &lt;div&gt;Student ID:  {{identification}}&lt;/div&gt;
      &lt;/template&gt;
  &lt;/dom-module&gt;
  </code></pre>
  
  <p>And when the ajax call finishes it will call <code>handleResponse</code> which will set <code>f_name</code>, <code>l_name</code>, <code>identification</code> variables.  The issue is that i see the variables are set in the last line of <code>handleResponse</code>.</p>
  
  <p>It doesn't set the markup according to say:   <code>First Name: Frank</code> at all, it is just empty.  I have determined that for some reason, <code>handleResponse</code> is a different scope than the other functions.  How do i fix this?</p>