Use Ash's ShelfWindowWatcher for app panel windows.

ash/common/shelf/shelf_item_types.h

 // Copyright 2014 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 ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_
 #define ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_
 
+#include <string>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace ash {
 
 typedef int ShelfID;
 
@@ skipping 46 matching lines @@
   ShelfItemType type = TYPE_UNDEFINED;
 
   // Image to display in the shelf.
   gfx::ImageSkia image;
 
   // Assigned by the model when the item is added.
   ShelfID id = kInvalidShelfID;
 
   // Running status.
   ShelfItemStatus status = STATUS_CLOSED;
+
+  // The application id for this shelf item; only populated for some items.
+  std::string app_id;
 };
 
 typedef std::vector<ShelfItem> ShelfItems;
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_