Fixs bug in notifying clients about hierarchy changes

services/ui/public/cpp/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 SERVICES_UI_PUBLIC_CPP_WINDOW_TREE_CLIENT_H_
 #define SERVICES_UI_PUBLIC_CPP_WINDOW_TREE_CLIENT_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 232 matching lines @@
   uint32_t ScheduleInFlightChange(std::unique_ptr<InFlightChange> change);
 
   // Returns true if there is an InFlightChange that matches |change|. If there
   // is an existing change SetRevertValueFrom() is invoked on it. Returns false
   // if there is no InFlightChange matching |change|.
   // See InFlightChange for details on how InFlightChanges are used.
   bool ApplyServerChangeToExistingInFlightChange(const InFlightChange& change);
 
   static Id server_id(const Window* window) { return window->server_id(); }
 
-  Window* BuildWindowTree(const mojo::Array<mojom::WindowDataPtr>& windows,
-                          Window* initial_parent);
+  void BuildWindowTree(const mojo::Array<mojom::WindowDataPtr>& windows,
+                       Window* initial_parent);
 
   Window* NewWindowImpl(NewWindowType type,
                         const Window::SharedProperties* properties);
 
   // Sets the mojom::WindowTree implementation.
   void SetWindowTree(mojom::WindowTreePtr window_tree_ptr);
 
   // Called when the mojom::WindowTree connection is lost, deletes this.
   void OnConnectionLost();
 
@@ skipping 223 matching lines @@
   std::set<Id> drag_entered_windows_;
 
   base::WeakPtrFactory<WindowTreeClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeClient);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_TREE_CLIENT_H_