Web shell test to go back and forward.

ios/web/shell/view_controller.mm

 // Copyright 2014 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.
 
 #import "ios/web/shell/view_controller.h"
 
 #include <stdint.h>
 
 #include <memory>
 #include <utility>
@@ skipping 115 matching lines @@
 
   NavigationManager::WebLoadParams params(GURL("https://dev.chromium.org/"));
   params.transition_type = ui::PAGE_TRANSITION_TYPED;
   self.navigationManager->LoadURLWithParams(params);
 }
 
 - (NavigationManager*)navigationManager {
   return _webState->GetNavigationManager();
 }
 
+- (web::WebState*)webState {
+  return _webState.get();
+}
+
 - (void)setUpNetworkStack {
   // Disable the default cache.
   [NSURLCache setSharedURLCache:[EmptyNSURLCache emptyNSURLCache]];
   net::CookieStoreIOS::SetCookiePolicy(net::CookieStoreIOS::ALLOW);
 }
 
 - (void)didReceiveMemoryWarning {
   [super didReceiveMemoryWarning];
 }
 
@@ skipping 106 matching lines @@
     (const web::LoadCommittedDetails&)details {
   [self updateToolbar];
 }
 
 - (void)webStateDidLoadPage:(web::WebState*)webState {
   DCHECK_EQ(_webState.get(), webState);
   [self updateToolbar];
 }
 
 @end