Added const getter for WebState's NavigationManager.

ios/web/public/web_state/web_state.h

 // Copyright 2013 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_PUBLIC_WEB_STATE_WEB_STATE_H_
 #define IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 106 matching lines @@
 
   // Gets the BrowserState associated with this WebState. Can never return null.
   virtual BrowserState* GetBrowserState() const = 0;
 
   // Opens a URL with the given disposition.  The transition specifies how this
   // navigation should be recorded in the history system (for example, typed).
   virtual void OpenURL(const OpenURLParams& params) = 0;
 
   // Gets the NavigationManager associated with this WebState. Can never return
   // null.
+  virtual const NavigationManager* GetNavigationManager() const = 0;
   virtual NavigationManager* GetNavigationManager() = 0;
 
   // Gets the CRWJSInjectionReceiver associated with this WebState.
   virtual CRWJSInjectionReceiver* GetJSInjectionReceiver() const = 0;
 
   // Runs JavaScript in the main frame's context. If a callback is provided, it
   // will be used to return the result, when the result is available or script
   // execution has failed due to an error.
   // NOTE: Integer values will be returned as TYPE_DOUBLE because of underlying
   // library limitation.
@@ skipping 125 matching lines @@
 
   // Returns a WeakPtr<WebState> to the current WebState. Must remain private
   // and only call must be in WebStateWeakPtrFactory. Please consult that class
   // for more details. Remove as part of http://crbug.com/556736.
   virtual base::WeakPtr<WebState> AsWeakPtr() = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_H_