title: How to bind object throw multi child elements
body: <p><strong>TLDR</strong>: How to define and upward pass a common property throw 3 registered elements?  </p>
  
  <p>Assume that you have a parent interface element and call it dashboard, now <code>&lt;dashboard&gt;</code> has a child element called <code>&lt;tree-node&gt;</code> which includes another child element inside it called <code>&lt;tree-node-element&gt;</code> which prompts the user to push some data into an array called chapters.</p>
  
  <p>How to pass chapters object from <code>&lt;tree-node-element&gt;</code> upwards to <code>&lt;dashboard&gt;</code>, should I define chapters property in each element, what flags should I give that property in each definition.</p>
  
  <p>Polymer V1x</p>