title: Polymer 1.0 paper-menu selected not working when scrolling to item in list
body: <p>I have the following code which works when selecting an item at the top of the list; however when scrolling down and selecting an element at the bottom of the list it reselects the pervious selected item.</p>
  
  <pre><code>&lt;div id="rolesDropDown" class="allRoles"&gt;
      &lt;paper-menu id="rolesMenu" selected="{{selectedIndex}}"&gt; 
          &lt;template is="dom-repeat" items="{{roles}}"&gt;
              &lt;div class="role"&gt;
                  &lt;div class="propName"&gt;&lt;span&gt;{{item.property.name}}&lt;/span&gt;&lt;/div&gt; 
                  &lt;div class="roleTitle" id="lightText"&gt;&lt;span&gt;{{item.title}}&lt;/span&gt;&lt;/div&gt; 
              &lt;/div&gt;
          &lt;/template&gt;
      &lt;/paper-menu&gt;
  &lt;/div&gt;
  </code></pre>
  
  <hr>
  
  <pre><code>selectedIndex:{
      type: Number,
      value: 0,
      notify: true,
      observer: "selectRole"
  }
  
  selectRole: function() { 
      console.log('inside select role method');
  }
  </code></pre>