mus: Makes ~WindowTreeClient reset context factory

ui/aura/mus/window_tree_client.h

 // Copyright 2014 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_MUS_WINDOW_TREE_CLIENT_H_
 #define UI_AURA_MUS_WINDOW_TREE_CLIENT_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 20 matching lines @@
 #include "ui/aura/mus/window_tree_host_mus_delegate.h"
 
 namespace display {
 class Display;
 }
 
 namespace gfx {
 class Insets;
 }
 
-namespace ui {
-struct PropertyData;
-}
-
 namespace service_manager {
 class Connector;
 }
 
 namespace ui {
+class ContextFactory;
 class Gpu;
+struct PropertyData;
 }
 
 namespace aura {
 class CaptureSynchronizer;
 class DragDropControllerMus;
 class FocusSynchronizer;
 class InFlightBoundsChange;
 class InFlightChange;
 class InFlightFocusChange;
 class InFlightPropertyChange;
@@ skipping 474 matching lines @@
   // The current change id for the window manager.
   uint32_t current_wm_move_loop_change_ = 0u;
   Id current_wm_move_loop_window_id_ = 0u;
 
   std::unique_ptr<DragDropControllerMus> drag_drop_controller_;
 
   base::ObserverList<WindowTreeClientTestObserver> test_observers_;
 
   std::unique_ptr<ui::Gpu> gpu_;
   std::unique_ptr<MusContextFactory> compositor_context_factory_;
+
+  // If |compositor_context_factory_| is installed on Env, then this is the
+  // ContextFactory that was set on Env originally.
+  ui::ContextFactory* initial_context_factory_ = nullptr;
   base::WeakPtrFactory<WindowTreeClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeClient);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_WINDOW_TREE_CLIENT_H_