PathLocationStrategy(PlatformLocation _platformLocation, [ @ @ String href ])

Source 

PathLocationStrategy(this._platformLocation,
    [@Optional() @Inject(APP_BASE_HREF) String href]) {
  href ??= this._platformLocation.getBaseHrefFromDOM();
  if (href == null) {
    throw new BaseException(
        '''No base href set. Please provide a value for the APP_BASE_HREF token or add a base element to the document.''');
  }
  this._baseHref = href;
}