Remove NavigationManager::GetPreviousItem().

ios/web/navigation/navigation_manager_impl.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_NAVIGATION_NAVIGATION_MANAGER_IMPL_H_
 #define IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 92 matching lines @@
   void AddPendingItem(const GURL& url,
                       const web::Referrer& referrer,
                       ui::PageTransition navigation_type,
                       NavigationInitiationType initiation_type);
 
   // Convenience accessors to get the underlying NavigationItems from the
   // SessionEntries returned from |session_controller_|'s -lastUserEntry and
   // -previousEntry methods.
   // TODO(crbug.com/546365): Remove these methods.
   NavigationItem* GetLastUserItem() const;
-  NavigationItem* GetPreviousItem() const;
 
   // Temporary method. Returns a vector of NavigationItems corresponding to
   // the SessionEntries of the uderlying CRWSessionController.
   // TODO(crbug.com/546365): Remove this method.
   NavigationItemList GetItems() const;
 
   // NavigationManager:
   BrowserState* GetBrowserState() const override;
   WebState* GetWebState() const override;
   NavigationItem* GetVisibleItem() const override;
@@ skipping 76 matching lines @@
   // List of transient url rewriters added by |AddTransientURLRewriter()|.
   std::unique_ptr<std::vector<BrowserURLRewriter::URLRewriter>>
       transient_url_rewriters_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationManagerImpl);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_IMPL_H_