mash: Remove WmWindow usage from ash/system/web_notification

ash/system/status_area_widget.cc

 // Copyright (c) 2012 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/system/status_area_widget.h"
 
 #include "ash/public/cpp/config.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_controller.h"
@@ skipping 183 matching lines @@
   overview_button_tray_->UpdateShelfItemBackground(color);
 }
 
 void StatusAreaWidget::AddSystemTray() {
   system_tray_ = new SystemTray(wm_shelf_);
   status_area_widget_delegate_->AddTray(system_tray_);
 }
 
 void StatusAreaWidget::AddWebNotificationTray() {
   DCHECK(system_tray_);
-  web_notification_tray_ = new WebNotificationTray(
-      wm_shelf_, WmWindow::Get(this->GetNativeWindow()), system_tray_);
+  web_notification_tray_ =
+      new WebNotificationTray(wm_shelf_, GetNativeWindow(), system_tray_);
   status_area_widget_delegate_->AddTray(web_notification_tray_);
 }
 
 void StatusAreaWidget::AddLockScreenActionTray() {
   DCHECK(system_tray_);
   lock_screen_action_tray_ = new LockScreenActionTray(wm_shelf_);
   status_area_widget_delegate_->AddTray(lock_screen_action_tray_);
 }
 
 void StatusAreaWidget::AddLogoutButtonTray() {
@@ skipping 15 matching lines @@
   ime_menu_tray_ = new ImeMenuTray(wm_shelf_);
   status_area_widget_delegate_->AddTray(ime_menu_tray_);
 }
 
 void StatusAreaWidget::AddOverviewButtonTray() {
   overview_button_tray_ = new OverviewButtonTray(wm_shelf_);
   status_area_widget_delegate_->AddTray(overview_button_tray_);
 }
 
 }  // namespace ash