Better Z-index support.

ui/aura/toplevel_window_container.h

+// Copyright (c) 2011 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_TOPLEVEL_WINDOW_CONTAINER_H_
+#define UI_AURA_TOPLEVEL_WINDOW_CONTAINER_H_
+#pragma once
+
+#include "ui/aura/window.h"
+
+namespace aura {
+namespace internal {
+
+class FocusManager;
+
+// A Window subclass that groups top-level windows.
+class ToplevelWindowContainer : public Window {
+ public:
+  ToplevelWindowContainer();
+  virtual ~ToplevelWindowContainer();
+
+  // Overridden from Window:
+  virtual bool IsToplevelWindowContainer() const OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ToplevelWindowContainer);
+};
+
+}  // namespace internal
+}  // namespace aura
+
+#endif  // UI_AURA_TOPLEVEL_WINDOW_CONTAINER_H_