mash: Cleanup ash shelf application menu code.

ash/common/shelf/app_list_shelf_item_delegate.cc

Index: ash/common/shelf/app_list_shelf_item_delegate.cc
diff --git a/ash/common/shelf/app_list_shelf_item_delegate.cc b/ash/common/shelf/app_list_shelf_item_delegate.cc
index 244d3e6128776f864fdfc8414640fc974df303f9..58118da8e659a7ceccdf0a13789499c82e20d64d 100644
--- a/ash/common/shelf/app_list_shelf_item_delegate.cc
+++ b/ash/common/shelf/app_list_shelf_item_delegate.cc
@@ -38,10 +38,10 @@ ShelfItemDelegate::PerformedAction AppListShelfItemDelegate::ItemSelected(
   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() {}