Use Ash's ShelfWindowWatcher for app panel windows.

ash/common/shelf/shelf_item_delegate.h

 // 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.
 
 #ifndef ASH_COMMON_SHELF_SHELF_ITEM_DELEGATE_H_
 #define ASH_COMMON_SHELF_SHELF_ITEM_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "base/strings/string16.h"
 
@@ skipping 52 matching lines @@
   // The caller takes ownership of the returned model.
   // |event_flags| specifies the flags of the event which triggered this menu.
   virtual ShelfMenuModel* CreateApplicationMenu(int event_flags) = 0;
 
   // Whether the launcher item is draggable.
   virtual bool IsDraggable() = 0;
 
   // Returns true if a tooltip should be shown.
   virtual bool ShouldShowTooltip() = 0;
 
+  // Returns true if this item is open.
+  virtual bool IsOpen() const = 0;
+
   // Closes all windows associated with this item.
   virtual void Close() = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_SHELF_ITEM_DELEGATE_H_