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

third_party/polymer/v1_0/components/iron-a11y-keys-behavior/iron-a11y-keys-behavior.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
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@@ skipping 76 matching lines @@
       46: 'del',
       106: '*'
     };
 
     /**
      * MODIFIER_KEYS maps the short name for modifier keys used in a key
      * combo string to the property name that references those same keys
      * in a KeyboardEvent instance.
      */
     var MODIFIER_KEYS = {
-      shift: 'shiftKey',
-      ctrl: 'ctrlKey',
-      alt: 'altKey',
-      meta: 'metaKey'
+      'shift': 'shiftKey',
+      'ctrl': 'ctrlKey',
+      'alt': 'altKey',
+      'meta': 'metaKey'
     };
 
     /**
      * KeyboardEvent.key is mostly represented by printable character made by
      * the keyboard, with unprintable keys labeled nicely.
      *
      * However, on OS X, Alt+char can make a Unicode character that follows an
      * Apple-specific mapping. In this case, we
      * fall back to .keyCode.
      */
@@ skipping 301 matching lines @@
         var detail = Object.create(keyCombo);
         detail.keyboardEvent = keyboardEvent;
 
         this[handlerName].call(this, new CustomEvent(keyCombo.event, {
           detail: detail
         }));
       }
     };
   })();
 </script>