mash: Cleanup ash shelf application menu code.

ash/common/shelf/app_list_shelf_item_delegate.cc

 // 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.
 
 #include "ash/common/shelf/app_list_shelf_item_delegate.h"
 
 #include "ash/common/shelf/shelf_model.h"
 #include "ash/common/wm_shell.h"
 #include "base/memory/ptr_util.h"
 #include "grit/ash_strings.h"
@@ skipping 20 matching lines @@
 AppListShelfItemDelegate::AppListShelfItemDelegate() {}
 
 AppListShelfItemDelegate::~AppListShelfItemDelegate() {}
 
 ShelfItemDelegate::PerformedAction AppListShelfItemDelegate::ItemSelected(
     const ui::Event& event) {
   WmShell::Get()->ToggleAppList();
   return ShelfItemDelegate::kAppListMenuShown;
 }
 
-ui::SimpleMenuModel* AppListShelfItemDelegate::CreateApplicationMenu(
+ShelfApplicationMenuItems AppListShelfItemDelegate::GetAppMenuItems(
     int event_flags) {
   // AppList does not show an application menu.
-  return nullptr;
+  return ShelfApplicationMenuItems();
 }
 
 void AppListShelfItemDelegate::Close() {}
 
 }  // namespace ash