anchor.diff:  
   library route.client;
   
  +import 'dart:collection';
   import 'dart:html';
   import 'package:logging/logging.dart';
   import 'url_pattern.dart';
  
positive.code:       window.history.pushState(null, title, path);
      }
    }
    
    /**
     * Returns an [Event] handler suitable for use as a click handler on [:<a>:]
     * elements. The handler reverses [ur] with [args] and uses [window.pushState]
  
negative.code:         if (e.target is AnchorElement) {
            AnchorElement anchor = e.target;
            if (anchor.host == window.location.host) {
              var fragment = (anchor.hash == '') ? '' : '${anchor.hash}';
              gotoPath("${anchor.pathname}$fragment", anchor.title);
              e.preventDefault();
            }
  