Update bower.json for Polymer elements and add PRESUBMIT.py

third_party/polymer/v1_0/components/neon-animation/animations/hero-animation.html

 <!--
 @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
 -->
 
@@ skipping 28 matching lines @@
 
     is: 'hero-animation',
 
     behaviors: [
       Polymer.NeonSharedElementAnimationBehavior
     ],
 
     configure: function(config) {
       var shared = this.findSharedElements(config);
       if (!shared) {
-        return null;
+        return;
       }
 
       var fromRect = shared.from.getBoundingClientRect();
       var toRect = shared.to.getBoundingClientRect();
 
       var deltaLeft = fromRect.left - toRect.left;
       var deltaTop = fromRect.top - toRect.top;
       var deltaWidth = fromRect.width / toRect.width;
       var deltaHeight = fromRect.height / toRect.height;
 
@@ skipping 14 matching lines @@
       if (!shared) {
         return null;
       }
       shared.to.style.zIndex = '';
       shared.from.style.visibility = '';
     }
 
   });
 
 </script>