chromeos: makes it possible for windows to outlive WindowTreeClient

ui/aura/mus/window_tree_client_unittest.cc

 // Copyright 2015 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 "ui/aura/mus/window_tree_client.h"
 
 #include <stdint.h>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 2387 matching lines @@
   EXPECT_EQ(ui::mojom::EventResult::HANDLED,
             window_tree()->GetEventResult(event_id));
   EXPECT_TRUE(window_delegate1.got_move());
   EXPECT_FALSE(window_delegate2.got_move());
   gfx::Point transformed_event_location_in_dip(event_location_in_dip.x() + 20,
                                                event_location_in_dip.y() + 30);
   EXPECT_EQ(transformed_event_location_in_dip,
             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