[third_party] add polymer 1.2.3

polymer_1.2.3/bower_components/iron-menu-behavior/demo/simple-menubar.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-menubar-behavior.html">
+<link rel="import" href="../../paper-styles/color.html">
 
 <dom-module id="simple-menubar">
 
   <style>
 
     .content ::content > .iron-selected {
-      color: red;
+      color: white;
+      background-color: var(--google-red-500);
     }
 
     .content ::content > * {
       display: inline-block;
     }
 
   </style>
 
   <template>
 
@@ skipping 15 matching lines @@
 
     behaviors: [
       Polymer.IronMenubarBehavior
     ]
 
   });
 
 })();
 
 </script>