title: Polymer 1.0 - Change Property Value Not Updated in Dom Repeat
body: <p>I have a <code>dom-repeat</code> element, and when this is rendered it only has a <code>name</code> property filled out, and the <code>price</code> will be populated by an ajax reponse:</p>
  
  <pre><code>&lt;template is="dom-repeat" id="myId" items="{{arr}}"&gt;
         &lt;div&gt;[[item.name]]&lt;/div&gt;
         &lt;div&gt;[[item.price]]&lt;/div&gt;
  &lt;/template&gt;
  </code></pre>
  
  <p>The problem is that the <code>price</code> isn't rendered after the response is gathered.</p>
  
  <p>I tried:</p>
  
  <pre><code>document.querySelector('#myId').render();
  </code></pre>
  
  <p>After the response has been received, but doesn't work. </p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>I can do <code>this.set('arr.x.price', value)</code> where <code>x</code> is the index of my object in the array, but my context is inside a function that does not know the index unless I calculate it, which isn't hard, but surely there must be a better way?</p>