Refactor and push window properties up to class properties.

ash/wm/window_properties.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 ASH_WM_WINDOW_PROPERTIES_H_
 #define ASH_WM_WINDOW_PROPERTIES_H_
 
 #include <stdint.h>
 
 #include "ash/ash_export.h"
 #include "ash/common/shelf/shelf_item_types.h"
+#include "ui/base/class_property.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace aura {
 template <typename T>
-struct WindowProperty;
+using WindowProperty = ui::ClassProperty<T>;
 }
 
 namespace ash {
 namespace wm {
 class WindowState;
 }  // namespace wm
 
 // Used with kWidgetCreationType to indicate source of the widget creation.
 enum class WidgetCreationType {
   // The widget was created internally, and not at the request of a client.
@@ skipping 51 matching lines @@
 
 // A property key to store WindowState in the window. The window state
 // is owned by the window.
 extern const aura::WindowProperty<wm::WindowState*>* const kWindowStateKey;
 
 // Alphabetical sort.
 
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_PROPERTIES_H_