After uninstall, remove last item in Launcher folder

ui/app_list/app_list_model.cc

 // Copyright (c) 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.
 
 #include "ui/app_list/app_list_model.h"
 
 #include <string>
 
 #include "ui/app_list/app_list_folder_item.h"
 #include "ui/app_list/app_list_item.h"
@@ skipping 201 matching lines @@
         dest_folder->item_list()->CreatePositionBefore(position));
     AddItemToFolderItemAndNotify(dest_folder, item_ptr.Pass());
   } else {
     item_ptr->set_position(
         top_level_item_list_->CreatePositionBefore(position));
     AddItemToItemListAndNotifyUpdate(item_ptr.Pass());
   }
   return true;
 }
 
+void AppListModel::DeleteUninstalledItem(const std::string& id) {
+  AppListItem* item = FindItem(id);
+  if (!item)
+    return;
+  AppListFolderItem* folder = FindFolderItem(item->folder_id());
+  DeleteItem(id);

[stevenjb, 2015/03/25 22:24:00]

What happens if this is the last item in a folder? Can DeleteItem cause the
folder to be deleted? It might be safer to save the folder_id and call
FindFolderItem(folder_id) after calling DeleteItem.

[Greg Levin, 2015/03/26 19:45:11]

Yes, good call.

+
+  // Issue 368111: Upon uninstall of 2nd-to-last folder item, reparent last item
+  // to top and remove folder.
+  if (folder && folder->ChildItemCount() == 1u) {
+    FOR_EACH_OBSERVER(AppListModelObserver, observers_,
+                      OnSingleItemFolderWillBeDeleted());
+
+    // Move last item in model, folder and views will update themselves.
+    AppListItem* last_item = folder->item_list()->item_at(0);
+    MoveItemToFolderAt(last_item, "", folder->position());
+  }
+}
+
 void AppListModel::SetItemPosition(AppListItem* item,
                                    const syncer::StringOrdinal& new_position) {
   if (!item->IsInFolder()) {
     top_level_item_list_->SetItemPosition(item, new_position);
     // Note: this will trigger OnListItemMoved which will signal observers.
     // (This is done this way because some View code still moves items within
     // the item list directly).
     return;
   }
   AppListFolderItem* folder = FindFolderItem(item->folder_id());
@@ skipping 203 matching lines @@
   scoped_ptr<AppListItem> result = folder->item_list()->RemoveItem(item->id());
   result->set_folder_id("");
   if (folder->item_list()->item_count() == 0) {
     DVLOG(2) << "Deleting empty folder: " << folder->ToDebugString();
     DeleteItem(folder_id);
   }
   return result.Pass();
 }
 
 }  // namespace app_list