Remove the concept of currentItemIndex

ios/chrome/browser/web/navigation_manager_util.mm

 // Copyright 2017 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/chrome/browser/web/navigation_manager_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 web::NavigationItem* GetLastNonRedirectedItem(
     web::NavigationManager* nav_manager) {
   if (!nav_manager || !nav_manager->GetItemCount())
     return nullptr;
-  int index = nav_manager->GetCurrentItemIndex();
+  int index = nav_manager->GetLastCommittedItemIndex();
   web::NavigationItem* item = nullptr;
   while (index >= 0) {
     item = nav_manager->GetItemAtIndex(index);
     // Returns the first non-Redirect item found.
     if ((item->GetTransitionType() & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) == 0)
       break;
     --index;
   }
   return item;
 }