chromeos: makes it possible for windows to outlive WindowTreeClient

ui/aura/test/aura_test_base.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_BASE_H_
 #define UI_AURA_TEST_AURA_TEST_BASE_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 46 matching lines @@
   }
 
   void set_window_tree_client_delegate(
       WindowTreeClientDelegate* window_tree_client_delegate) {
     window_tree_client_delegate_ = window_tree_client_delegate;
   }
 
   // Turns on mus with a test WindowTree. Must be called before SetUp().
   void EnableMusWithTestWindowTree();
 
+  // 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();
+
   // Used to configure the backend. This is exposed to make parameterized tests
   // easy to write. This *must* be called from SetUp().
   void ConfigureBackend(BackendType type);
 
   void RunAllPendingInMessageLoop();
 
   void ParentWindow(Window* window);
 
   // A convenience function for dispatching an event to |dispatcher()|.
   // Returns whether |event| was handled.
@@ skipping 104 matching lines @@
   void SetUp() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AuraTestBaseMus);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_AURA_TEST_BASE_H_