message: Stored url in history state against a key
  This makes room for a user spreading in their own state values, e.g.,
  const state = {...window.history.state, userValue: 3};
  window.history.replaceState(state, null);
diff: @@ -11,7 +11,7 @@ class HTML5HistoryManager implements HistoryManager {
  init(navigateHistory: (url?: string) => void) {
  if (!this.disabled && !this.navigateHistory) {
  - this.navigateHistory = e => navigateHistory(e.state || undefined);
  + this.navigateHistory = e => navigateHistory((e.state && e.state.navigationLink) || undefined);
  window.addEventListener('popstate', this.navigateHistory);
  }
  }
  @@ -20,9 +20,9 @@ class HTML5HistoryManager implements HistoryManager {
  var href = this.getHref(url);
  if (!this.disabled && this.getHref(this.getUrl(window.location)) !== href) {
  if (!replace)
  - window.history.pushState(url, null, href);
  + window.history.pushState({navigationLink: url}, null, href);
  else
  - window.history.replaceState(url, null, href);
  + window.history.replaceState({navigationLink: url}, null, href);
  }
  }
  