update polymer

dashboard-ui/bower_components/webcomponentsjs/ShadowDOM.js

@@ -7,7 +7,7 @@
  * 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
  */
-// @version 0.7.17
+// @version 0.7.18
 if (typeof WeakMap === "undefined") {
   (function() {
     var defineProperty = Object.defineProperty;
@@ -1131,7 +1131,8 @@ window.ShadowDOMPolyfill = {};
       Object.defineProperty(this, "defaultPrevented", {
         get: function() {
           return true;
-        }
+        },
+        configurable: true
       });
     };
   }