Create a common directory of widgets and css.

appengine/chromium_rietveld/new_static/common/cr-dialog.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. -->
 
 <link rel="import" href="cr-dialog-backdrop.html">
 <link rel="import" href="cr-keyboard.html">
 
 <polymer-element name="cr-dialog" extends="dialog">
     <template>
         <style>
@@ skipping 46 matching lines @@
                 this.fireCancelEvent = function(event) {
                     event.preventDefault();
                     if (!this.fire("cancel").defaultPrevented)
                         this.close();
                 };
             },
         });
     })();
     </script>
 </ploymer-element>