implement user agent override option.

ios/web/public/test/fakes/test_navigation_manager.h

 // 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.
 
 #ifndef IOS_WEB_PUBLIC_TEST_FAKES_TEST_NAVIGATION_MANAGER_H_
 #define IOS_WEB_PUBLIC_TEST_FAKES_TEST_NAVIGATION_MANAGER_H_
 
 #import "ios/web/public/navigation_item.h"
 #include "ios/web/public/navigation_item_list.h"
 #import "ios/web/public/navigation_manager.h"
@@ skipping 27 matching lines @@
   bool CanGoForward() const override;
   bool CanGoToOffset(int offset) const override;
   void GoBack() override;
   void GoForward() override;
   void GoToIndex(int index) override;
   void Reload(ReloadType reload_type, bool check_for_reposts) override;
   NavigationItemList GetBackwardItems() const override;
   NavigationItemList GetForwardItems() const override;
   void CopyStateFromAndPrune(const NavigationManager* source) override;
   bool CanPruneAllButLastCommittedItem() const override;
-  void OverrideDesktopUserAgentForNextPendingItem() override;
 
   // Setters for test data.
   // Sets a value for last committed item that will be returned by
   // GetLastCommittedItem().
   void SetLastCommittedItem(NavigationItem* item);
 
   // Sets a value for pending item that will be returned by GetPendingItem().
   void SetPendingItem(NavigationItem* item);
 
   // Sets a value for visible item that will be returned by GetVisibleItem().
@@ skipping 13 matching lines @@
   int items_index_;
   // Individual backing instance variables for Set* test set up methods.
   NavigationItem* pending_item_;
   NavigationItem* last_committed_item_;
   NavigationItem* visible_item_;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_TEST_FAKES_TEST_NAVIGATION_MANAGER_H_