title: Polymer. Update view after model changed
body: <p>This is a common question in Polymer about updating view when model was updated (answer is to use this.set or this.push Polymer methods). </p>
  
  <p>But when I have two elements:</p>
  
  <p>First element:</p>
  
  <pre><code>properties:{
    items: {
      type: Array
    }
  },
  
  someFunction: {
    this.push('items', {'Name': 'something'});
  }
  </code></pre>
  
  <p>Second Element has property which is bound to 'items' from first element</p>
  
  <pre><code>ready: function(){
      this.items = firstElement.items;
  }
  </code></pre>
  
  <p>I would like second element 'items' to be updated when 'items' updated on firstElement. I can't manually notify secondElement, because of app restrictions.</p>
  
  <p>So for now I see (in devTools) that model of second element is correct ('items' contains objects), but view isn't updated.  </p>
  
  <p>How to update it? </p>