mash: Move SystemTrayDelegate ownership to WmShell

ash/system/chromeos/supervised/tray_supervised_user_unittest.cc

 // 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.
 
 #include "ash/system/chromeos/supervised/tray_supervised_user.h"
 
-#include "ash/shell.h"
 #include "ash/system/user/login_status.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/test/test_system_tray_delegate.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_list.h"
 #include "ui/message_center/notification_types.h"
 
 using message_center::NotificationList;
 
@@ skipping 38 matching lines @@
   test::TestSystemTrayDelegate::SetInitialLoginStatus(LoginStatus::SUPERVISED);
   test::AshTestBase::SetUp();
 }
 
 void TraySupervisedUserInitialTest::TearDown() {
   test::AshTestBase::TearDown();
   // SetInitialLoginStatus() is reset in AshTestHelper::TearDown().
 }
 
 TEST_F(TraySupervisedUserTest, SupervisedUserHasNotification) {
-  test::TestSystemTrayDelegate* delegate =
-      static_cast<test::TestSystemTrayDelegate*>(
-          ash::Shell::GetInstance()->system_tray_delegate());
+  test::TestSystemTrayDelegate* delegate = GetSystemTrayDelegate();
   delegate->SetLoginStatus(LoginStatus::SUPERVISED);
 
   message_center::Notification* notification = GetPopup();
   ASSERT_NE(static_cast<message_center::Notification*>(NULL), notification);
   EXPECT_EQ(static_cast<int>(message_center::SYSTEM_PRIORITY),
             notification->rich_notification_data().priority);
 }
 
 TEST_F(TraySupervisedUserInitialTest, SupervisedUserNoCrash) {
   // Initial login status is already SUPERVISED, which should create
   // the notification and should not cause crashes.
   message_center::Notification* notification = GetPopup();
   ASSERT_NE(static_cast<message_center::Notification*>(NULL), notification);
   EXPECT_EQ(static_cast<int>(message_center::SYSTEM_PRIORITY),
             notification->rich_notification_data().priority);
 }
 
-}  // namespace
+}  // namespace ash