Disable folder UI when app sync is disabled

ui/app_list/views/apps_grid_view.h

 // 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.
 
 #ifndef UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_
 #define UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_
 
 #include <set>
 #include <string>
 
@@ skipping 192 matching lines @@
   }
 
   void set_folder_delegate(AppsGridViewFolderDelegate* folder_delegate) {
     folder_delegate_ = folder_delegate;
   }
 
   AppListItemView* activated_folder_item_view() const {
     return activated_folder_item_view_;
   }
 
+  const AppListModel* model() const { return model_; }
+
  private:
   friend class test::AppsGridViewTestApi;
 
   enum DropAttempt {
     DROP_FOR_NONE,
     DROP_FOR_REORDER,
     DROP_FOR_FOLDER,
   };
 
   // Represents the index to an item view in the grid.
@@ skipping 324 matching lines @@
 
   // True if the drag_view_ item is a folder item being dragged for reparenting.
   bool dragging_for_reparent_item_;
 
   DISALLOW_COPY_AND_ASSIGN(AppsGridView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_