Fix white flash when user sings out and wallpaper animation regression

ash/root_window_controller.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/root_window_controller.h"
 
 #include <vector>
 
 #include "ash/desktop_background/desktop_background_widget_controller.h"
 #include "ash/display/display_controller.h"
@@ skipping 269 matching lines @@
 }
 
 void RootWindowController::CreateContainers() {
   CreateContainersInRootWindow(root_window_.get());
 }
 
 void RootWindowController::CloseChildWindows() {
   // Close background widget first as it depends on tooltip.
   root_window_->SetProperty(kWindowDesktopComponent,
       static_cast<DesktopBackgroundWidgetController*>(NULL));
+  root_window_->SetProperty(kComponentWrapper,
+                            static_cast<ComponentWrapper*>(NULL));
 
   workspace_controller_.reset();
   aura::client::SetTooltipClient(root_window_.get(), NULL);
 
   while (!root_window_->children().empty()) {
     aura::Window* child = root_window_->children()[0];
     delete child;
   }
 }
 
@@ skipping 22 matching lines @@
   // Restore focused or active window if it's still alive.
   if (focused && tracker.Contains(focused) && dst->Contains(focused)) {
     dst->GetFocusManager()->SetFocusedWindow(focused, NULL);
   } else if (active && tracker.Contains(active) && dst->Contains(active)) {
     activation_client->ActivateWindow(active);
   }
 }
 
 }  // namespace internal
 }  // namespace ash