title: How to tell when Polymer is done with all the data-binding?
body: <p>Let's say I have a Polymer element <code>x-foo</code> which uses templates for data-binding.</p>
  
  <pre><code>&lt;template&gt;
    &lt;!--shadow DOM--&gt;
    &lt;template repeat='{{item in items}}'&gt;
      &lt;div class='content'&gt;{{item}}&lt;/div&gt;
    &lt;/template&gt;
  &lt;/template&gt;
  </code></pre>
  
  <p><code>items</code> is a property of <code>x-foo</code> which decides what is present in the view.</p>
  
  <p>Now, on the fly <strong>in one of the methods</strong> of <code>x-foo</code> I do:</p>
  
  <pre><code>this.items = getNewItemList();
  </code></pre>
  
  <p>and then try to access shadow DOM content,</p>
  
  <pre><code>this.shadowRoot.querySelectorAll('.content') // was supposed to return 5 elements
  </code></pre>
  
  <p>I find that Polymer still hasn't iterated through the template loop and generated my shadow DOM content. Is there a way to know when it has finished it?</p>