reland of https://codereview.chromium.org/11364053/ w/o removing the per-rootwindow stacking client

chrome/browser/ui/aura/stacking_client_aura.h

Index: chrome/browser/ui/aura/stacking_client_aura.h
diff --git a/chrome/browser/ui/aura/stacking_client_aura.h b/chrome/browser/ui/aura/stacking_client_aura.h
new file mode 100644
index 0000000000000000000000000000000000000000..9bbd5a4f9f01c7f68028c8e3a45b8cf1dfd5423c
--- /dev/null
+++ b/chrome/browser/ui/aura/stacking_client_aura.h
@@ -0,0 +1,42 @@
+// 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 CHROME_BROWSER_UI_AURA_STACKING_CLIENT_AURA_H_
+#define CHROME_BROWSER_UI_AURA_STACKING_CLIENT_AURA_H_
+
+#include "ui/aura/client/stacking_client.h"
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/ui/host_desktop.h"
+
+namespace ash {
+class StackingController;
+}
+
+namespace aura {
+class DesktopStackingClient;
+class Window;
+}
+
+// A stacking client for the two worlds aura, dispatches to either a
+// DesktopStackingClient or an ash::StackingController.
+class StackingClientAura : public aura::client::StackingClient {
+ public:
+  StackingClientAura();
+  virtual ~StackingClientAura();
+
+  // Overridden from client::StackingClient:
+  virtual aura::Window* GetDefaultParent(aura::Window* context,
+                                         aura::Window* window,
+                                         const gfx::Rect& bounds) OVERRIDE;
+
+ private:
+  scoped_ptr<aura::DesktopStackingClient> desktop_stacking_client_;
+
+  DISALLOW_COPY_AND_ASSIGN(StackingClientAura);
+};
+
+#endif  // CHROME_BROWSER_UI_AURA_STACKING_CLIENT_AURA_H_