mash: Move SystemTrayDelegate ownership to WmShell

ash/system/web_notification/web_notification_tray_unittest.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/web_notification/web_notification_tray.h"
 
 #include <utility>
 #include <vector>
 
 #include "ash/common/shell_window_ids.h"
@@ skipping 268 matching lines @@
 #define MAYBE_PopupAndSystemTrayMultiDisplay \
   DISABLED_PopupAndSystemTrayMultiDisplay
 #endif
 
 // Verifies if the notification appears on both displays when extended mode.
 TEST_F(WebNotificationTrayTest, MAYBE_PopupShownOnBothDisplays) {
   if (!SupportsMultipleDisplays())
     return;
 
   // Enables to appear the notification for display changes.
-  test::TestSystemTrayDelegate* tray_delegate =
-      static_cast<test::TestSystemTrayDelegate*>(
-          Shell::GetInstance()->system_tray_delegate());
+  test::TestSystemTrayDelegate* tray_delegate = GetSystemTrayDelegate();
   tray_delegate->set_should_show_display_notification(true);
 
   UpdateDisplay("400x400,200x200");
   // UpdateDisplay() creates the display notifications, so popup is visible.
   EXPECT_TRUE(GetTray()->IsPopupVisible());
   WebNotificationTray* secondary_tray = GetSecondaryTray();
   ASSERT_TRUE(secondary_tray);
   EXPECT_TRUE(secondary_tray->IsPopupVisible());
 
   // Transition to mirroring and then back to extended display, which recreates
@@ skipping 238 matching lines @@
   ui::TouchEvent release(ui::ET_TOUCH_RELEASED, out_of_bounds, touch_id,
       move.time_stamp()+base::TimeDelta::FromMilliseconds(50));
   generator.Dispatch(&release);
   EXPECT_FALSE(tray->draw_background_as_active());
   EXPECT_FALSE(tray->IsMessageCenterBubbleVisible());
 }
 
 #endif  // OS_CHROMEOS
 
 }  // namespace ash