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

ui/aura/event_filter.cc

 // 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.
 
 #include "ui/aura/event_filter.h"
 
 #include "ui/aura/desktop.h"
 #include "ui/aura/event.h"
 #include "ui/aura/focus_manager.h"
 #include "ui/aura/window.h"
@@ skipping 24 matching lines @@
 void EventFilter::ActivateIfNecessary(
     Window* window,
     MouseEvent* event) {
   // TODO(beng): some windows (e.g. disabled ones, tooltips, etc) may not be
   //             focusable.
 
   Window* active_window = Desktop::GetInstance()->active_window();
   Window* toplevel_window = window;
   while (toplevel_window && toplevel_window != active_window &&
          toplevel_window->parent() &&
-         !toplevel_window->parent()->IsToplevelWindowContainer()) {
+         !toplevel_window->parent()->AsToplevelWindowContainer()) {
     toplevel_window = toplevel_window->parent();
   }
   if (toplevel_window == active_window) {
     // |window| is a descendant of the active window, no need to activate.
     window->GetFocusManager()->SetFocusedWindow(window);
     return;
   }
   if (!toplevel_window) {
     // |window| is not in a top level window.
     return;
   }
   if (!toplevel_window->delegate() ||
       !toplevel_window->delegate()->ShouldActivate(event))
     return;
 
   Desktop::GetInstance()->SetActiveWindow(toplevel_window, window);
 }
 
 }  // namespace aura