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

ui/views/widget/native_widget_layer_reorderer_aura.h

+// Copyright (c) 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 UI_VIEWS_WIDGET_NATIVE_WIDGET_LAYER_REORDERER_AURA_H_
+#define UI_VIEWS_WIDGET_NATIVE_WIDGET_LAYER_REORDERER_AURA_H_
+
+#include "base/compiler_specific.h"
+#include "ui/aura/window_observer.h"
+
+namespace aura {
+class Window;
+}
+
+namespace views {
+class View;
+
+// Class which ensures the following z-order of the widget's child layers from
+// topmost to bottommost:
+// 1) Layers for child windows with a NULL layer delegate.
+// 2) Layers for views and layers for child windows attached to a view ordered
+//    according to the order of the views in the view hierarchy.
+// 3) Layers for child windows not attached to a view and layers not owned by
+//    a window or a view.
+// The order of child windows is kept in sync with the order of the layers.
+class NativeWidgetLayerReordererAura : public aura::WindowObserver {
+ public:
+  NativeWidgetLayerReordererAura(aura::Window* window, View* root_view);
+  virtual ~NativeWidgetLayerReordererAura();
+
+  // Explicitly reorder |window_|'s child layers. This method should be called
+  // when the view hierarchy changes.
+  void ReorderLayers();
+
+ private:
+  // Stop observing |window| and its children.
+  void StopObserving(aura::Window* window);
+
+  // aura::WindowObserver overrides:
+  virtual void OnWindowAdded(aura::Window* new_window) OVERRIDE;
+  virtual void OnWillRemoveWindow(aura::Window* window) OVERRIDE;
+  virtual void OnWindowPropertyChanged(aura::Window* window,
+                                       const void* key,
+                                       intptr_t old) OVERRIDE;
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
+  // The window and the root view of the native widget which owns the
+  // NativeWidgetLayerReordererAura.
+  aura::Window* window_;
+  View* root_view_;
+
+  DISALLOW_COPY_AND_ASSIGN(NativeWidgetLayerReordererAura);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_WIDGET_NATIVE_WIDGET_LAYER_REORDERER_AURA_H_