Change active root window before closing old root windows' children.

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 9854d36a909a684c052bf5dcf9fd415781b5e1ad..27f0a0144d48736b8a5c70a49245e94c768a8636 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -271,12 +271,17 @@ void RootWindowController::Shutdown() {
   wallpaper_controller_.reset();
   animating_wallpaper_controller_.reset();
 
-  CloseChildWindows();
+  // Change the active root window before closing child windows. If any child
+  // being removed triggers a relayout of the shelf it will try to build a
+  // window list adding windows from the active root window's containers which
+  // may have already gone away.
   if (Shell::GetActiveRootWindow() == root_window_) {
     Shell::GetInstance()->set_active_root_window(
         Shell::GetPrimaryRootWindow() == root_window_.get() ?
         NULL : Shell::GetPrimaryRootWindow());
   }
+
+  CloseChildWindows();
   SetRootWindowController(root_window_.get(), NULL);
   screen_dimmer_.reset();
   workspace_controller_.reset();