Create a common directory of widgets and css.

appengine/chromium_rietveld/new_static/common/cr-hash-observer.html

 <!-- Copyright (c) 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file. -->
 
 <!--
     Use to observe to dynamically observe changes to the hash in the url.
 
     ex.
         <cr-hash-observer on-hash-changed="{{ handleHashChange }}"></cr-hash-observer>
 -->
@@ skipping 30 matching lines @@
 
         function handleHashChange() {
             setTimeout(notifyInstancesIfNeeded);
         }
 
         document.addEventListener("navigate", handleHashChange);
         window.addEventListener("hashchange", handleHashChange);
     })();
     </script>
 </polymer-element>