Remove NavigationManager::GetPreviousItem().

ios/chrome/browser/tabs/tab_model.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/chrome/browser/tabs/tab_model.h"
 
 #include <cstdint>
 #include <utility>
 #include <vector>
 
@@ skipping 729 matching lines @@
   // to WebStateList, this function will return a std::unique_ptr<> and the
   // object destroyed as expected, so it will fine to ignore the result then
   // too. See http://crbug.com/546222 for progress of changing the ownership
   // of the WebStates.
   ignore_result(_webStateList.DetachWebStateAt(closedTabIndex));
 
   if (needToSaveSession)
     [self saveSessionImmediately:NO];
 }
 
-- (void)navigationCommittedInTab:(Tab*)tab {
+- (void)navigationCommittedInTab:(Tab*)tab
+                    previousItem:(web::NavigationItem*)previousItem {
   if (self.offTheRecord)
     return;
   if (![tab navigationManager])
     return;
 
   // See if the navigation was within a page; if so ignore it.
-  web::NavigationItem* previousItem =
-      [tab navigationManagerImpl]->GetPreviousItem();
   if (previousItem) {
     GURL previousURL = previousItem->GetURL();
     GURL currentURL = [tab navigationManager]->GetVisibleItem()->GetURL();
 
     url::Replacements<char> replacements;
     replacements.ClearRef();
     if (previousURL.ReplaceComponents(replacements) ==
         currentURL.ReplaceComponents(replacements)) {
       return;
     }
@@ skipping 186 matching lines @@
 }
 
 // Called when UIApplicationWillEnterForegroundNotification is received.
 - (void)applicationWillEnterForeground:(NSNotification*)notify {
   if (_tabUsageRecorder) {
     _tabUsageRecorder->AppWillEnterForeground();
   }
 }
 
 @end