Add ios_web_view_shell_egtests target and accessibility labels to shell.

ios/web_view/shell/shell_view_controller.h

 // 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.
 
 #ifndef IOS_WEB_VIEW_SHELL_SHELL_VIEW_CONTROLLER_H_
 #define IOS_WEB_VIEW_SHELL_SHELL_VIEW_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/web_view/public/cwv_navigation_delegate.h"
 #import "ios/web_view/public/cwv_ui_delegate.h"
 
+// Accessibility label added to the back button.
+extern NSString* const kWebViewShellBackButtonAccessibilityLabel;
+// Accessibility label added to the forward button.
+extern NSString* const kWebViewShellForwardButtonAccessibilityLabel;
+// Accessibility label added to the URL address text field.
+extern NSString* const kWebViewShellAddressFieldAccessibilityLabel;
 // Accessibility identifier added to the text field of JavaScript prompts.
 extern NSString* const
     kWebViewShellJavaScriptDialogTextFieldAccessibiltyIdentifier;
 
 // Implements the main UI for web_view_shell, including the toolbar and web
 // view.
 @interface ShellViewController : UIViewController
 
 @end
 
 #endif  // IOS_WEB_VIEW_SHELL_SHELL_VIEW_CONTROLLER_H_