chromeos: makes it possible for windows to outlive WindowTreeClient

ui/aura/mus/window_tree_client_unittest.cc

Index: ui/aura/mus/window_tree_client_unittest.cc
diff --git a/ui/aura/mus/window_tree_client_unittest.cc b/ui/aura/mus/window_tree_client_unittest.cc
index 2f8b467f1f09c6b9a237080ed6fb75126312294e..8de08458a08a45d5be596bcf7975fc2523d66908 100644
--- a/ui/aura/mus/window_tree_client_unittest.cc
+++ b/ui/aura/mus/window_tree_client_unittest.cc
@@ -2405,4 +2405,14 @@ TEST_F(WindowTreeClientClientTestHighDPI, InputEventsInDip) {
             window_delegate1.last_event_location());
 }
 
+using WindowTreeClientDestructionTest = test::AuraTestBaseMus;
+
+TEST_F(WindowTreeClientDestructionTest, Shutdown) {
+  aura::Window window(nullptr);
+  window.Init(ui::LAYER_NOT_DRAWN);
+  DeleteWindowTreeClient();
+  aura::Window window2(nullptr);
+  window2.Init(ui::LAYER_NOT_DRAWN);
+}
+
 }  // namespace aura