Enable hide animation for login screen.

ash/shell.cc

 // 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.
 
 #include "ash/shell.h"
 
 #include <algorithm>
 
 #include "ash/accelerators/accelerator_controller.h"
 #include "ash/accelerators/accelerator_filter.h"
@@ skipping 98 matching lines @@
   modal_container->set_id(internal::kShellWindowId_SystemModalContainer);
   SetChildWindowVisibilityChangesAnimated(modal_container);
   containers->push_back(modal_container);
 
   // TODO(beng): Figure out if we can make this use
   // SystemModalContainerEventFilter instead of stops_event_propagation.
   aura::Window* lock_container = new aura::Window(NULL);
   lock_container->SetLayoutManager(new internal::BaseLayoutManager);
   lock_container->set_stops_event_propagation(true);
   lock_container->set_id(internal::kShellWindowId_LockScreenContainer);
-  SetChildWindowVisibilityChangesAnimated(lock_container);
   containers->push_back(lock_container);
 
   aura::Window* lock_modal_container = new aura::Window(NULL);
   lock_modal_container->SetEventFilter(
       new ToplevelWindowEventFilter(lock_modal_container));
   lock_modal_container->SetLayoutManager(
       new internal::SystemModalContainerLayoutManager(lock_modal_container));
   lock_modal_container->set_id(
       internal::kShellWindowId_LockSystemModalContainer);
   SetChildWindowVisibilityChangesAnimated(lock_modal_container);
@@ skipping 378 matching lines @@
 
   // Create the desktop background image.
   root_window_layout_->SetBackgroundWidget(internal::CreateDesktopBackground());
 }
 
 void Shell::ResetLayoutManager(int container_id) {
   GetContainer(container_id)->SetLayoutManager(NULL);
 }
 
 }  // namespace ash