anchor.diff:     * 5. Starts monitoring [Route] parameters for changes and automatically
      *    updates the [url] with [History.replaceState].
      */
  -  void navigate(url) {
  +  void navigate(url, [withoutPush = false]) {
       var match = this.router.match(url);
       this.transitionHandler(
         this.views[activeRoute],
  
positive.code:       match[1]
      );
      this.activeRoute = match[0];
      this.history.pushState(null, '', url);
  
      // Stop watching parameters of the previous view.
      if (this.activeWatchDisposer != null) {
  
negative.code:     ev.preventDefault();
    });
  
    window.onPopState.listen(
      (e) => navigator.navigate(window.location.pathname, true)
    );
  
    // Initialize routing with current url.
    navigator.navigate(window.location.pathname);
  
  