chromeos: makes it possible for windows to outlive WindowTreeClient

ui/aura/test/aura_test_helper.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_AURA_TEST_AURA_TEST_HELPER_H_
 #define UI_AURA_TEST_AURA_TEST_HELPER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 42 matching lines @@
   // Makes aura target mus with a mock WindowTree (TestWindowTree). Must be
   // called before SetUp().
   void EnableMusWithTestWindowTree(
       WindowTreeClientDelegate* window_tree_delegate,
       WindowManagerDelegate* window_manager_delegate);
 
   // Makes aura target mus with the specified WindowTreeClient. Must be called
   // before SetUp().
   void EnableMusWithWindowTreeClient(WindowTreeClient* window_tree_client);
 
+  // Deletes the WindowTreeClient now. Normally the WindowTreeClient is deleted
+  // at the right time and there is no need to call this. This is provided for
+  // testing shutdown ordering.
+  void DeleteWindowTreeClient();
+
   // Creates and initializes (shows and sizes) the RootWindow for use in tests.
   void SetUp(ui::ContextFactory* context_factory,
              ui::ContextFactoryPrivate* context_factory_private);
 
   // Clean up objects that are created for tests. This also deletes the Env
   // object.
   void TearDown();
 
   // Flushes message loop.
   void RunAllPendingInMessageLoop();
@@ skipping 50 matching lines @@
 
   WindowTreeClient* window_tree_client_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(AuraTestHelper);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_AURA_TEST_HELPER_H_