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 169 matching lines @@
 - (void)updateToolbar {
   // Do not update the URL if the text field is currently being edited.
   if ([_field isFirstResponder]) {
     return;
   }
 
   const GURL& visibleURL = _webState->GetVisibleURL();
   [_field setText:base::SysUTF8ToNSString(visibleURL.spec())];
 }
 
+- (web::WebState*)webState {
+  return _webState.get();
+}
+
 // -----------------------------------------------------------------------
 #pragma mark Bikeshedding Implementation
 
 // Overridden to allow this view controller to receive motion events by being
 // first responder when no other views are.
 - (BOOL)canBecomeFirstResponder {
   return YES;
 }
 
 - (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent*)event {
@@ skipping 52 matching lines @@
     (const web::LoadCommittedDetails&)details {
   [self updateToolbar];
 }
 
 - (void)webStateDidLoadPage:(web::WebState*)webState {
   DCHECK_EQ(_webState.get(), webState);
   [self updateToolbar];
 }
 
 @end