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third_party/polymer/components/iron-overlay-behavior/test/test-overlay2.html

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 @license
 Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 Code distributed by Google as part of the polymer project is also
 subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
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 <link rel="import" href="../../polymer/polymer.html">
 
 <link rel="import" href="../iron-overlay-behavior.html">
 
 <dom-module id="test-overlay2">
 
   <style>
 
     :host {
       background: white;
       color: black;
       border: 1px solid black;
     }
 
   </style>
 
   <template>
+    <button id="first">first</button>
     <content></content>
+    <button id="last">last</button>
   </template>
 
 </dom-module>
 
 <script>
 
 (function() {
 
   Polymer({
 
     is: 'test-overlay2',
 
     behaviors: [
       Polymer.IronOverlayBehavior
-    ]
+    ],
+    
+    get _focusableNodes() {
+      return [this.$.first, this.$.last];
+    }
 
   });
 
 })();
 
 </script>