arc: Fix crash on window close (on close race condition).

chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc

Index: chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
diff --git a/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc b/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
index af304775a7bad41b9f6425ec39d8d0e1f8ebfd76..d622f7be90fe4b0fca7507ea59e31b8f5b3209f9 100644
--- a/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
@@ -338,8 +338,10 @@ void ArcAppWindowLauncherController::OnWindowDestroying(aura::Window* window) {
   window->RemoveObserver(this);
 
   for (auto& it : task_id_to_app_window_) {
-    if (it.second->widget() == views::Widget::GetWidgetForNativeWindow(window))
-      it.second->set_widget(nullptr);
+    if (it.second->GetNativeWindow() == window) {
+      OnTaskDestroyed(it.second->task_id());
+      break;
+    }
   }
 }