Fixes shutdown race in mash

ash/mus/test/wm_test_helper.cc

 // 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.
 
 #include "ash/mus/test/wm_test_helper.h"
 
 #include "ash/mus/root_window_controller.h"
 #include "ash/mus/test/wm_test_screen.h"
 #include "ash/mus/window_manager.h"
 #include "ash/mus/window_manager_application.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "components/mus/public/cpp/property_type_converters.h"
 #include "components/mus/public/cpp/tests/window_tree_client_private.h"
 #include "components/mus/public/cpp/window_tree_client.h"
 #include "ui/display/display.h"
 
 namespace ash {
 namespace mus {
 
 WmTestHelper::WmTestHelper() {}
 
 WmTestHelper::~WmTestHelper() {}
 
 void WmTestHelper::Init() {
   message_loop_.reset(new base::MessageLoopForUI());
-  window_manager_app_.window_manager_.reset(
-      new WindowManager(&window_manager_app_, nullptr));
+  window_manager_app_.window_manager_.reset(new WindowManager(nullptr));
   screen_ = new WmTestScreen;
   window_manager_app_.window_manager_->screen_.reset(screen_);
 
   // Need an id other than kInvalidDisplayID so the Display is considered valid.
   display::Display display(1);
   const gfx::Rect display_bounds(0, 0, 800, 600);
   display.set_bounds(display_bounds);
   // Offset the height slightly to give a different work area. -20 is arbitrary,
   // it could be anything.
   const gfx::Rect work_area(0, 0, display_bounds.width(),
                             display_bounds.height() - 20);
   display.set_work_area(work_area);
   window_tree_client_setup_.InitForWindowManager(
       window_manager_app_.window_manager_.get(),
       window_manager_app_.window_manager_.get(), display);
 
   window_manager_app_.InitWindowManager(
       window_tree_client_setup_.window_tree_client());
 
   screen_->display_list()->AddDisplay(display,
                                       views::DisplayList::Type::PRIMARY);
 
   ::mus::WindowTreeClientPrivate(window_tree_client_setup_.window_tree_client())
       .CallWmNewDisplayAdded(display);
 }
 
 }  // namespace mus
 }  // namespace ash