goog.require('goog.dom');
  goog.require('goog.events');
  goog.require('goog.History');

/*
  var h = new goog.History();
  goog.events.listen(h, goog.History.EventType.NAVIGATE, navCallback);
  h.setEnabled(true);
 
  function setToken(opt_val) {
    var input = goog.dom.getElement('token_input');
    h.setToken(opt_val || input.value);
    return false;
  }
 
  function replaceToken() {
    var input = goog.dom.getElement('token_input');
    h.replaceToken(input.value);
  }
 
  function navCallback(e) {
    var output = goog.dom.getElement('token_output');
    if (output) {
      var token = (e.token == null) ? 'null' : '\u201C' + e.token + '\u201D';
      goog.dom.setTextContent(output, token);
    }
  }
*/