Reorder the NativeViews attached to a view via kViewHostKey according to the position of the view

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 "ui/aura/aura_export.h"
 #include "ui/aura/window.h"
 #include "ui/base/ui_base_types.h"
 
 namespace ui {
 class InputMethod;
 }
 
+namespace views {
+class View;
+}
+
 namespace aura {
 namespace client {
 
 // Alphabetical sort.
 
 // A property key to store always-on-top flag.
 AURA_EXPORT extern const WindowProperty<bool>* const kAlwaysOnTopKey;
 
 // A property key to store whether animations are disabled for the window. Type
 // of value is an int.
 AURA_EXPORT extern const WindowProperty<bool>* const kAnimationsDisabledKey;
 
 // A property key to store the can-maximize flag.
 AURA_EXPORT extern const WindowProperty<bool>* const kCanMaximizeKey;
 
 // A property key to store the can-resize flag.
 AURA_EXPORT extern const WindowProperty<bool>* const kCanResizeKey;
 
 // A property key to store if a window is a constrained window or not.
 AURA_EXPORT extern const WindowProperty<bool>* const kConstrainedWindowKey;
 
 // A property key to indicate that a window should show that it deserves
 // attention.
 AURA_EXPORT extern const aura::WindowProperty<bool>* const kDrawAttentionKey;
 
+// A property key to indicate the window's host view. If specified, the host
+// view determines the z-order of the window in its parent widget. The host
+// view must have the same parent widget as the window on which the property
+// is set. The z-order of the window is set to the z-order of the host view in
+// the view tree relative to:
+// - views with layers.
+// - views bound to a window via the kHostViewKey.
+AURA_EXPORT extern const WindowProperty<views::View*>* const kHostViewKey;
+
 // A property key to store the window modality.
 AURA_EXPORT extern const WindowProperty<ui::ModalType>* const kModalKey;
 
 // A property key to store the restore bounds for a window.
 AURA_EXPORT extern const WindowProperty<gfx::Rect*>* const kRestoreBoundsKey;
 
 // A property key to store ui::WindowShowState for restoring a window.
 // Used in Ash to remember the show state before the window was minimized.
 AURA_EXPORT extern const WindowProperty<ui::WindowShowState>* const
     kRestoreShowStateKey;
 
 // A property key to store an input method object that handles a key event.
 AURA_EXPORT extern const WindowProperty<ui::InputMethod*>* const
     kRootWindowInputMethodKey;
 
 // A property key to store ui::WindowShowState for a window.
 // See ui/base/ui_base_types.h for its definition.
 AURA_EXPORT extern const WindowProperty<ui::WindowShowState>* const
     kShowStateKey;
 
 // Alphabetical sort.
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_AURA_CONSTANTS_H_