Use Ash's ShelfWindowWatcher for app panel windows.

ui/aura/client/aura_constants.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_AURA_CLIENT_AURA_CONSTANTS_H_
 #define UI_AURA_CLIENT_AURA_CONSTANTS_H_
 
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/aura/aura_export.h"
 #include "ui/aura/window.h"
@@ skipping 65 matching lines @@
 
 // The inset of the topmost view in the client view from the top of the
 // non-client view. The topmost view depends on the window type. The topmost
 // view is the tab strip for tabbed browser windows, the toolbar for popups,
 // the web contents for app windows and varies for fullscreen windows.
 AURA_EXPORT extern const aura::WindowProperty<int>* const kTopViewInset;
 
 // The color of the window header.
 AURA_EXPORT extern const aura::WindowProperty<SkColor>* const kTopViewColor;
 
-// A property key to store window icon.
+// A property key to store the window icon, typically 16x16 for title bars.
 AURA_EXPORT extern const WindowProperty<gfx::ImageSkia*>* const kWindowIconKey;
 
+// A property key to store the app icon, typically larger for shelf icons, etc.
+AURA_EXPORT extern const WindowProperty<gfx::ImageSkia*>* const kAppIconKey;
+
 // Alphabetical sort.
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_AURA_CONSTANTS_H_