Remove NavigationManager::GetPreviousItem().

ios/web/navigation/navigation_manager_impl_unittest.mm

 // Copyright 2014 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/navigation_manager_impl.h"
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
 #import "ios/web/navigation/crw_session_controller+private_constructors.h"
 #import "ios/web/navigation/navigation_manager_delegate.h"
@@ skipping 33 matching lines @@
   TestBrowserState browser_state_;
   TestNavigationManagerDelegate delegate_;
   std::unique_ptr<NavigationManagerImpl> manager_;
   base::scoped_nsobject<CRWSessionController> controller_;
 };
 
 // Tests state of an empty navigation manager.
 TEST_F(NavigationManagerTest, EmptyManager) {
   EXPECT_EQ(0, navigation_manager()->GetItemCount());
   EXPECT_EQ(-1, navigation_manager()->GetCurrentItemIndex());
-  EXPECT_FALSE(navigation_manager()->GetPreviousItem());
   EXPECT_EQ(-1, navigation_manager()->GetCurrentItemIndex());
   EXPECT_FALSE(navigation_manager()->GetPendingItem());
   EXPECT_EQ(-1, navigation_manager()->GetPendingItemIndex());
   EXPECT_EQ(-1, navigation_manager()->GetIndexForOffset(0));
 }
 
 // Tests that GetPendingItemIndex() returns -1 if there is no pending entry.
 TEST_F(NavigationManagerTest, GetPendingItemIndexWithoutPendingEntry) {
   navigation_manager()->AddPendingItem(
       GURL("http://www.url.com"), Referrer(), ui::PAGE_TRANSITION_TYPED,
@@ skipping 444 matching lines @@
   navigation_manager()->OverrideDesktopUserAgentForNextPendingItem();
   navigation_manager()->AddPendingItem(
       GURL("http://www.url.com"), Referrer(), ui::PAGE_TRANSITION_TYPED,
       web::NavigationInitiationType::USER_INITIATED);
   [session_controller() commitPendingItem];
   NavigationItem* visible_item = navigation_manager()->GetVisibleItem();
   EXPECT_TRUE(visible_item->IsOverridingUserAgent());
 }
 
 }  // namespace web