mash: Port TrayUpdateTest to AshTest

ash/common/wm_shell.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/common/wm_shell.h"
 
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
 #include "ash/common/accelerators/ash_focus_manager_factory.h"
@@ skipping 316 matching lines @@
   return delegate_->GetAppListPresenter()->GetTargetVisibility();
 }
 
 void WmShell::SetKeyboardUI(std::unique_ptr<KeyboardUI> keyboard_ui) {
   keyboard_ui_ = std::move(keyboard_ui);
 }
 
 void WmShell::SetSystemTrayDelegate(
     std::unique_ptr<SystemTrayDelegate> delegate) {
   DCHECK(delegate);
-  DCHECK(!system_tray_delegate_);
-  // TODO(jamescook): Create via ShellDelegate once it moves to //ash/common.
   system_tray_delegate_ = std::move(delegate);
   system_tray_delegate_->Initialize();
 #if defined(OS_CHROMEOS)
   logout_confirmation_controller_.reset(new LogoutConfirmationController(
       base::Bind(&SystemTrayDelegate::SignOut,
                  base::Unretained(system_tray_delegate_.get()))));
 #endif
 }
 
 void WmShell::DeleteSystemTrayDelegate() {
@@ skipping 31 matching lines @@
 void WmShell::DeleteToastManager() {
   toast_manager_.reset();
 }
 
 void WmShell::SetAcceleratorController(
     std::unique_ptr<AcceleratorController> accelerator_controller) {
   accelerator_controller_ = std::move(accelerator_controller);
 }
 
 }  // namespace ash