index.html

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    
    <!-- Polymer imports -->
    <script>Polymer = {dom: 'shadow'};</script>
    <link rel="import" href="elements/browser-topbar/browser-topbar.html">
    <link rel="import" href="elements/browser-header/browser-header.html">
    <link rel="import" href="elements/browser-content/browser-content.html">
  
    <!-- Native styles -->
    <link rel="stylesheet" href="chrome://resources/css/text_defaults.css">
    <link rel="stylesheet" href="chrome://resources/css/roboto.css">

    <!-- App global resources -->
    <link rel="stylesheet" href="index.css">
    <script type="text/javascript" src="index.js"></script>
  </head>

  <body>
    <browser-topbar></browser-topbar>
    <browser-header></browser-header>

    <browser-content></browser-content>
  </body>
</html>