Adds NavigationManager util functions to ios/chrome/browser/web/

ios/web/navigation/crw_session_controller.mm

 // Copyright 2012 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/web/navigation/crw_session_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 188 matching lines @@
 - (web::NavigationItemImpl*)lastCommittedItem {
   NSInteger index = self.currentNavigationIndex;
   return index == -1 ? nullptr : self.items[index].get();
 }
 
 - (web::NavigationItemImpl*)previousItem {
   NSInteger index = self.previousNavigationIndex;
   return index == -1 || self.items.empty() ? nullptr : self.items[index].get();
 }
 
-- (web::NavigationItemImpl*)lastUserItem {
-  if (self.items.empty())
-    return nil;
-
-  NSInteger index = self.currentNavigationIndex;
-  // This will return the first NavigationItem if all other items are
-  // redirects, regardless of the transition state of the first item.
-  while (index > 0 && [self isRedirectTransitionForItemAtIndex:index])
-    --index;
-
-  return self.items[index].get();
-}
-
 - (web::NavigationItemList)backwardItems {
   web::NavigationItemList items;
   for (size_t index = _currentNavigationIndex; index > 0; --index) {
     if (![self isRedirectTransitionForItemAtIndex:index])
       items.push_back(self.items[index - 1].get());
   }
   return items;
 }
 
 - (web::NavigationItemList)forwardItems {
@@ skipping 407 matching lines @@
   return item;
 }
 
 - (BOOL)isRedirectTransitionForItemAtIndex:(size_t)index {
   DCHECK_LT(index, self.items.size());
   ui::PageTransition transition = self.items[index]->GetTransitionType();
   return (transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) ? YES : NO;
 }
 
 @end