Remove NavigationManager::GetPreviousItem().

ios/web/navigation/navigation_manager_impl.mm

 // 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.
 
 #import "ios/web/navigation/navigation_manager_impl.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 121 matching lines @@
   if (facade_delegate_)
     facade_delegate_->OnNavigationItemChanged();
 }
 
 void NavigationManagerImpl::OnNavigationItemCommitted() {
   LoadCommittedDetails details;
   details.item = GetLastCommittedItem();
   DCHECK(details.item);
   details.previous_item_index = [session_controller_ previousNavigationIndex];
   if (details.previous_item_index >= 0) {
-    DCHECK(GetPreviousItem());
-    details.previous_url = GetPreviousItem()->GetURL();
+    DCHECK([session_controller_ previousItem]);
+    details.previous_url = [session_controller_ previousItem]->GetURL();
     details.is_in_page =
         AreURLsInPageNavigation(details.previous_url, details.item->GetURL());
   } else {
     details.previous_url = GURL();
     details.is_in_page = NO;
   }
 
   delegate_->OnNavigationItemCommitted(details);
 
   if (facade_delegate_) {
@@ skipping 32 matching lines @@
          GetLastCommittedItem()->IsOverridingUserAgent());
     GetPendingItem()->SetIsOverridingUserAgent(use_desktop_user_agent);
     override_desktop_user_agent_for_next_pending_item_ = false;
   }
 }
 
 NavigationItem* NavigationManagerImpl::GetLastUserItem() const {
   return [session_controller_ lastUserItem];
 }
 
-NavigationItem* NavigationManagerImpl::GetPreviousItem() const {
-  return [session_controller_ previousItem];
-}
-
 NavigationItemList NavigationManagerImpl::GetItems() const {
   return [session_controller_ items];
 }
 
 BrowserState* NavigationManagerImpl::GetBrowserState() const {
   return browser_state_;
 }
 
 WebState* NavigationManagerImpl::GetWebState() const {
   return delegate_->GetWebState();
@@ skipping 32 matching lines @@
     BrowserURLRewriter::URLRewriter rewriter) {
   DCHECK(rewriter);
   if (!transient_url_rewriters_) {
     transient_url_rewriters_.reset(
         new std::vector<BrowserURLRewriter::URLRewriter>());
   }
   transient_url_rewriters_->push_back(rewriter);
 }
 
 int NavigationManagerImpl::GetItemCount() const {
-  return GetItems().size();
+  return [session_controller_ itemCount];
 }
 
 NavigationItem* NavigationManagerImpl::GetItemAtIndex(size_t index) const {
-  NavigationItemList items = GetItems();
-  return index < items.size() ? items[index] : nullptr;
+  return [session_controller_ itemAtIndex:index];
 }
 
 int NavigationManagerImpl::GetCurrentItemIndex() const {
   return [session_controller_ currentNavigationIndex];
 }
 
 int NavigationManagerImpl::GetPendingItemIndex() const {
   if (GetPendingItem()) {
     if ([session_controller_ pendingItemIndex] != -1) {
       return [session_controller_ pendingItemIndex];
     }
     // TODO(crbug.com/665189): understand why current item index is
     // returned here.
     return GetCurrentItemIndex();
   }
   return -1;
 }
 
 int NavigationManagerImpl::GetLastCommittedItemIndex() const {
-  if (GetItems().empty())
+  if (GetItemCount() == 0)
     return -1;
   return [session_controller_ currentNavigationIndex];
 }
 
 bool NavigationManagerImpl::RemoveItemAtIndex(int index) {
   if (index == GetLastCommittedItemIndex() || index == GetPendingItemIndex())
     return false;
 
-  size_t idx = static_cast<size_t>(index);
-  if (idx >= GetItems().size())
+  if (index < 0 || index >= GetItemCount())
     return false;
 
   [session_controller_ removeItemAtIndex:index];
   return true;
 }
 
 bool NavigationManagerImpl::CanGoBack() const {
   return CanGoToOffset(-1);
 }
 
@@ skipping 111 matching lines @@
 }
 
 bool NavigationManagerImpl::IsRedirectItemAtIndex(int index) const {
   DCHECK_GT(index, 0);
   DCHECK_LT(index, GetItemCount());
   ui::PageTransition transition = GetItemAtIndex(index)->GetTransitionType();
   return transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK;
 }
 
 }  // namespace web