mash: Fold ShelfItemDelegateManager into ShelfModel

ash/common/shelf/app_list_shelf_item_delegate.h

Index: ash/common/shelf/app_list_shelf_item_delegate.h
diff --git a/ash/common/shelf/app_list_shelf_item_delegate.h b/ash/common/shelf/app_list_shelf_item_delegate.h
index 07a51fd829b57ad2f31d8cf00c3a89bafbc7a579..bb8e1f094faae6d9380d60e7b2cbeb034cb1dd07 100644
--- a/ash/common/shelf/app_list_shelf_item_delegate.h
+++ b/ash/common/shelf/app_list_shelf_item_delegate.h
@@ -9,12 +9,16 @@
 #include "base/macros.h"
 
 namespace ash {
+class ShelfModel;
 
 // ShelfItemDelegate for TYPE_APP_LIST.
 class AppListShelfItemDelegate : public ShelfItemDelegate {
  public:
-  AppListShelfItemDelegate();
+  // Initializes the app list item in the shelf data model and creates an
+  // AppListShelfItemDelegate which will be owned by |shelf_model|.
+  static void CreateAppListItemAndDelegate(ShelfModel* shelf_model);
 
+  AppListShelfItemDelegate();
   ~AppListShelfItemDelegate() override;
 
   // ShelfItemDelegate: