anchor.diff:  class Local { // TODO: find a better name.
     dynamic _handler;
   
  -  // The window is injected to make the class testable through mocks.
  -  Window _window;
  -
  -  Local(this._handler, [this._window]) {
  -    if (_window == null) _window = window;
  -
  -    _window.onPopState.listen(_onWindowLocationChange);
  +  Local(this._handler) {
  +    window.onPopState.listen(_onWindowLocationChange);
   
       // Handle the initial window location.
       _onWindowLocationChange();
  
positive.code: /**
   * Implements the dart:html Shelf adapter.
   */
  Future<Local> serve(handler, [Window window]) {
    return new Future.value(new Local(handler, window));
  }
negative.code:    * [_onWindowLocationChange] event handler.
     */
    void go(String path, {Map state: const {}, String title: ''}) {
      window.history.pushState(state, title, path);
      _onWindowLocationChange();
    }
  
    void _onWindowLocationChange([PopStateEvent e]) {
      final request = new Request('GET', new Uri(scheme: 'http', path: window.location.pathname));
      _handler(request).then((Response response) {
        switch (response.statusCode) {
          // If the statusCode of the  response is 30x perform an 'internal redirect'
  