Moves some shutdown related code to earlier on in function

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 2051fc13d3917c19ff467d5654b704bc209f1c0a..c5a9a6241c6edcee719371833b4abd9a8929536e 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -537,6 +537,10 @@ void RootWindowController::OnWallpaperAnimationFinished(views::Widget* widget) {
 }
 
 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_|
@@ -560,9 +564,6 @@ void RootWindowController::CloseChildWindows() {
     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?

@@ -570,7 +571,6 @@ void RootWindowController::CloseChildWindows() {
   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.