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

ui/aura_shell/aura_shell.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
 
   'targets': [
@@ skipping 21 matching lines @@
         # All .cc, .h under views, except unittests
         'desktop_background_view.cc',
         'desktop_background_view.h',
         'desktop_layout_manager.cc',
         'desktop_layout_manager.h',
         'desktop_window.cc',
         'launcher/launcher_view.cc',
         'launcher/launcher_view.h',
         'launcher/launcher_button.cc',
         'launcher/launcher_button.h',
+        'shell.cc',
+        'shell.h',
         'shell_factory.h',
         'shell_window_ids.h',
         'status_area_view.cc',
         'status_area_view.h',
         'toplevel_frame_view.cc',
         'toplevel_frame_view.h',
       ],
     },
     {
       'target_name': 'aura_shell_unittests',
@@ skipping 71 matching lines @@
         '../../views/views.gyp:views_desktop',
         '../../views/views.gyp:views_desktop_lib',
         '../../views/views.gyp:views_unittests',
         '../aura/aura.gyp:*',
         '../gfx/compositor/compositor.gyp:*',
         'aura_shell_exe',
       ],
     },
   ],
 }