code: public static void set (String path, int expires, String name, String value)
      {
          set(path, expires, name, value, getTopPrivateDomain(Window.Location.getHostName()));
      }
docs: Sets a cross-domain cookie to the supplied value, which can be accessed by other subdomains.
  If the current hostname is foo.bar.com, the cookie will be set on the .bar.com domain. If it
  is foo.bar.baz.com, it will be set on the .baz.com domain. If it is bar.com, it will be set
  on the .bar.com domain. If it is localhost (or any other non-domain-looking hostname), no
  domain will be specified.
  
  @param expires The number of days in which the cookie should expire.