change the way windows are parented when their parent is set to NULL.

ui/aura/test_desktop_delegate.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_TEST_DESKTOP_DELEGATE_H_
+#define UI_AURA_TEST_DESKTOP_DELEGATE_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/aura/desktop_delegate.h"
+#include "ui/aura/toplevel_window_container.h"
+
+namespace aura {
+
+class ToplevelWindowContainer;
+
+class TestDesktopDelegate : public DesktopDelegate {
+ public:
+  TestDesktopDelegate();
+  virtual ~TestDesktopDelegate();
+
+  Window* default_container() { return default_container_.get(); }
+
+ private:
+  // Overridden from DesktopDelegate:
+  virtual void AddChildToDefaultParent(Window* window) OVERRIDE;
+  virtual Window* GetTopmostWindowToActivate(Window* ignore) const OVERRIDE;
+
+  scoped_ptr<ToplevelWindowContainer> default_container_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestDesktopDelegate);
+};
+
+}  // namespace aura
+
+#endif  // UI_AURA_TEST_DESKTOP_DELEGATE_H_