Moves some shutdown related code to earlier on in function

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 <queue>
 #include <vector>
 
 #include "ash/aura/aura_layout_manager_adapter.h"
@@ skipping 519 matching lines @@
   if (animating_wallpaper_widget_controller()) {
     WallpaperWidgetController* controller =
         animating_wallpaper_widget_controller()->GetController(true);
     DCHECK_EQ(controller->widget(), widget);
     // Release the old controller and close its wallpaper widget.
     SetWallpaperWidgetController(controller);
   }
 }
 
 void RootWindowController::CloseChildWindows() {
+  aura::Window* root_window = GetRootWindow();
+  aura::client::SetDragDropClient(root_window, nullptr);
+  aura::client::SetTooltipClient(root_window, nullptr);
+
   mouse_event_target_.reset();
 
   // Remove observer as deactivating keyboard causes |docked_layout_manager_|
   // to fire notifications.
   if (docked_layout_manager_ && wm_shelf_aura_->shelf_layout_manager()) {
     docked_layout_manager_->RemoveObserver(
         wm_shelf_aura_->shelf_layout_manager());
   }
 
   // Deactivate keyboard container before closing child windows and shutting
   // down associated layout managers.
   DeactivateKeyboard(keyboard::KeyboardController::GetInstance());
 
   // panel_layout_manager_ needs to be shut down before windows are destroyed.
   if (panel_layout_manager_) {
     panel_layout_manager_->Shutdown();
     panel_layout_manager_ = NULL;
   }
   // docked_layout_manager_ needs to be shut down before windows are destroyed.
   if (docked_layout_manager_) {
     docked_layout_manager_->Shutdown();
     docked_layout_manager_ = NULL;
   }
-  aura::Window* root_window = GetRootWindow();
-  aura::client::SetDragDropClient(root_window, NULL);
-
   wm_shelf_aura_->ShutdownShelfWidget();
 
   // Close wallpaper widget first as it depends on tooltip.

[James Cook, 2016/09/07 21:41:45]

This comment seems concerning. If it's no longer true, please remove it.

Also, msw has a CL in-flight that touches this code,
https://codereview.chromium.org/2318223003

[sky, 2016/09/07 22:02:27]

Good point. I moved to end. Take another look?

   wallpaper_widget_controller_.reset();
   animating_wallpaper_widget_controller_.reset();
 
   wm_root_window_controller_->DeleteWorkspaceController();
-  aura::client::SetTooltipClient(root_window, NULL);
 
   // Explicitly destroy top level windows. We do this as during part of
   // destruction such windows may query the RootWindow for state.
   aura::WindowTracker non_toplevel_windows;
   non_toplevel_windows.Add(root_window);
   while (!non_toplevel_windows.windows().empty()) {
     const aura::Window* non_toplevel_window =
         *non_toplevel_windows.windows().begin();
     non_toplevel_windows.Remove(const_cast<aura::Window*>(non_toplevel_window));
     aura::WindowTracker toplevel_windows;
@@ skipping 366 matching lines @@
     aura::Window* primary_root_window = Shell::GetInstance()
                                             ->window_tree_host_manager()
                                             ->GetPrimaryRootWindow();
     return GetRootWindowSettings(primary_root_window)->controller;
   }
 
   return GetRootWindowSettings(root_window)->controller;
 }
 
 }  // namespace ash