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

ui/aura/desktop.cc

Index: ui/aura/desktop.cc
===================================================================
--- ui/aura/desktop.cc	(revision 104542)
+++ ui/aura/desktop.cc	(working copy)
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/message_loop.h"
+#include "ui/aura/desktop_delegate.h"
 #include "ui/aura/desktop_host.h"
 #include "ui/aura/focus_manager.h"
 #include "ui/aura/root_window.h"
@@ -24,13 +25,11 @@
 ui::Compositor*(*Desktop::compositor_factory_)() = NULL;
 
 Desktop::Desktop()
-    : default_parent_(NULL),
+    : delegate_(NULL),
       host_(aura::DesktopHost::Create(gfx::Rect(200, 200, 1280, 1024))),
       ALLOW_THIS_IN_INITIALIZER_LIST(schedule_paint_(this)),
       active_window_(NULL),
       in_destructor_(false) {
-  DCHECK(MessageLoopForUI::current())
-      << "The UI message loop must be initialized first.";
   if (compositor_factory_) {
     compositor_ = (*Desktop::compositor_factory())();
   } else {
@@ -55,15 +54,6 @@
   compositor()->SetRootLayer(window_->layer());
 }
 
-void Desktop::CreateDefaultParentForTesting() {
-  Window* default_parent = new internal::ToplevelWindowContainer;
-  default_parent->Init();
-  default_parent->SetBounds(window_->bounds());
-  default_parent->Show();
-  window_->AddChild(default_parent);
-  set_default_parent(default_parent);
-}
-
 void Desktop::Show() {
   host_->Show();
 }
@@ -125,7 +115,7 @@
 }
 
 void Desktop::ActivateTopmostWindow() {
-  SetActiveWindow(GetTopmostWindowToActivate(NULL), NULL);
+  SetActiveWindow(delegate_->GetTopmostWindowToActivate(NULL), NULL);
 }
 
 void Desktop::WindowDestroying(Window* window) {
@@ -135,7 +125,7 @@
   // Reset active_window_ before invoking SetActiveWindow so that we don't
   // attempt to notify it while running its destructor.
   active_window_ = NULL;
-  SetActiveWindow(GetTopmostWindowToActivate(window), NULL);
+  SetActiveWindow(delegate_->GetTopmostWindowToActivate(window), NULL);
 }
 
 MessageLoop::Dispatcher* Desktop::GetDispatcher() {
@@ -143,17 +133,6 @@
 }
 
 
-Window* Desktop::GetTopmostWindowToActivate(Window* ignore) {
-  Window::Windows windows(default_parent_->children());
-  for (Window::Windows::const_reverse_iterator i = windows.rbegin();
-       i != windows.rend(); ++i) {
-    if (*i != ignore && (*i)->IsVisible() &&
-        (*i)->delegate()->ShouldActivate(NULL))
-      return *i;
-  }
-  return NULL;
-}
-
 // static
 Desktop* Desktop::GetInstance() {
   if (!instance_) {