Fixes bug in handling window deletion originating from server

ui/aura/mus/window_port_mus.h

 // Copyright 2016 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_PORT_MUS_H_
 #define UI_AURA_MUS_WINDOW_PORT_MUS_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 90 matching lines @@
   //
   // And the call from the Window (by way of WindowPort interface) looks like:
   //   ServerChangeData change_data;
   //   change_data.foo = ...;
   //   if (!RemoveChangeByTypeAndData(ServerChangeType::FOO, change_data))
   //     window_tree_client_->OnFooChanged(this, ...);
   enum ServerChangeType {
     ADD,
     ADD_TRANSIENT,
     BOUNDS,
+    DESTROY,
     PROPERTY,
     REMOVE,
     REMOVE_TRANSIENT,
     REORDER,
     VISIBLE,
   };
 
   // Contains data needed to identify a change from the server.
   struct ServerChangeData {
     // Applies to ADD, ADD_TRANSIENT, REMOVE, REMOVE_TRANSIENT and REORDER.
@@ skipping 64 matching lines @@
                          ui::mojom::OrderDirection) override;
   void SetBoundsFromServer(const gfx::Rect& bounds) override;
   void SetVisibleFromServer(bool visible) override;
   void SetOpacityFromServer(float opacity) override;
   void SetPredefinedCursorFromServer(ui::mojom::Cursor cursor) override;
   void SetPropertyFromServer(
       const std::string& property_name,
       const std::vector<uint8_t>* property_data) override;
   void SetSurfaceIdFromServer(
       std::unique_ptr<SurfaceInfo> surface_info) override;
+  void DestroyFromServer() override;
   void AddTransientChildFromServer(WindowMus* child) override;
   void RemoveTransientChildFromServer(WindowMus* child) override;
   ChangeSource OnTransientChildAdded(WindowMus* child) override;
   ChangeSource OnTransientChildRemoved(WindowMus* child) override;
   std::unique_ptr<WindowMusChangeData> PrepareForServerBoundsChange(
       const gfx::Rect& bounds) override;
   std::unique_ptr<WindowMusChangeData> PrepareForServerVisibilityChange(
       bool value) override;
   void NotifyEmbeddedAppDisconnected() override;
 
@@ skipping 22 matching lines @@
   std::unique_ptr<SurfaceInfo> surface_info_;
 
   ui::mojom::Cursor predefined_cursor_ = ui::mojom::Cursor::CURSOR_NULL;
 
   DISALLOW_COPY_AND_ASSIGN(WindowPortMus);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_WINDOW_PORT_MUS_H_