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

third_party/polymer/v1_0/components/paper-styles/shadow.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
 -->
 
 <link rel="import" href="../polymer/polymer.html">
 
 <style is="custom-style">
 
   :root {
 
     --shadow-transition: {
       transition: box-shadow 0.28s cubic-bezier(0.4, 0, 0.2, 1);
     };
 
+    --shadow-none: {
+      box-shadow: none;
+    };
+
     /* from http://codepen.io/shyndman/pen/c5394ddf2e8b2a5c9185904b57421cdb */
 
     --shadow-elevation-2dp: {
       box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.14),
                   0 1px 5px 0 rgba(0, 0, 0, 0.12),
                   0 3px 1px -2px rgba(0, 0, 0, 0.2);
     };
 
     --shadow-elevation-3dp: {
       box-shadow: 0 3px 4px 0 rgba(0, 0, 0, 0.14),
@@ skipping 21 matching lines @@
 
     --shadow-elevation-16dp: {
       box-shadow: 0 16px 24px 2px rgba(0, 0, 0, 0.14),
                   0  6px 30px 5px rgba(0, 0, 0, 0.12),
                   0  8px 10px -5px rgba(0, 0, 0, 0.4);
     };
 
   }
 
 </style>