Add functionality to window.history.go test page.

ios/testing/data/http_server_files/history_go.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Adds event listeners and populates on-load-div.
 window.onload = function() {
   window.addEventListener('popstate', onPopstate);
   window.addEventListener('hashchange', onHashChange);
   updateOnLoadText('OnLoadText');
 };
 
 // Populates pop-state-received-div and state-object-div upon a popstate event.
 var onPopstate = function(e) {
   updatePopStateReceivedText(true);
-  updateStateObjectText(e.state);
+  var stateText = e.state ? e.state : '(NO STATE OBJECT)';
+  updateStateObjectText(stateText);
 };
 
 // Populates hash-change-received-div upon receiving of a hashchange event.
 var onHashChange = function(e) {
   updateHashChangeReceivedText(true);
 }
 
 var updateOnLoadText = function(text) {
   document.getElementById('on-load-div').innerHTML = text;
 }
@@ skipping 31 matching lines @@
 var goNoParameter = function() {
   onButtonTapped();
   window.history.go();
 }
 
 var goZero = function() {
   onButtonTapped();
   window.history.go(0);
 }
 
+var goBack = function() {
+  onButtonTapped();
+  window.history.back();
+}
+
+var goForward = function() {
+  onButtonTapped();
+  window.history.forward();
+}
+
 var go2 = function() {
   onButtonTapped();
   window.history.go(2);
 }
 
 var goBack2 = function() {
   onButtonTapped();
   window.history.go(-2);
 }
+
+var pushStateWithHash = function() {
+  onButtonTapped();
+  window.history.pushState('STATE_OBJECT', 'Title', '#hash');
+}