mash: Convert TrayBackgroundView to wm common types

ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc

Index: ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc
diff --git a/ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc b/ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc
index 591b31e4ddf31cbe15d6199a508bbc4e529f45c6..e939f956df3ffe7e9dd556a9cb494012e73ed388 100644
--- a/ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc
+++ b/ash/system/tray/media_security/multi_profile_media_tray_item_unittest.cc
@@ -5,12 +5,13 @@
 #include "ash/system/tray/media_security/multi_profile_media_tray_item.h"
 
 #include "ash/ash_view_ids.h"
+#include "ash/common/system/tray/system_tray_bubble.h"
 #include "ash/common/system/tray/tray_item_view.h"
-#include "ash/shell.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/system_tray.h"
-#include "ash/system/tray/system_tray_bubble.h"
 #include "ash/test/ash_test_base.h"
+#include "ash/test/ash_test_helper.h"
+#include "ash/test/status_area_widget_test_helper.h"
 #include "ash/test/test_session_state_delegate.h"
 #include "ash/test/test_shell_delegate.h"
 #include "ui/views/bubble/tray_bubble_view.h"
@@ -22,19 +23,18 @@ typedef test::AshTestBase MultiProfileMediaTrayItemTest;
 TEST_F(MultiProfileMediaTrayItemTest, NotifyMediaCaptureChange) {
   TrayItemView::DisableAnimationsForTest();
   test::TestShellDelegate* shell_delegate =
-      static_cast<test::TestShellDelegate*>(Shell::GetInstance()->delegate());
+      ash_test_helper()->test_shell_delegate();
   test::TestSessionStateDelegate* session_state_delegate =
-      static_cast<test::TestSessionStateDelegate*>(
-          Shell::GetInstance()->session_state_delegate());
+      test::AshTestHelper::GetTestSessionStateDelegate();
   session_state_delegate->set_logged_in_users(2);
 
-  SystemTray* system_tray = Shell::GetInstance()->GetPrimarySystemTray();
+  SystemTray* system_tray = GetPrimarySystemTray();
   system_tray->ShowDefaultView(BUBBLE_CREATE_NEW);
   views::View* in_user_view =
       system_tray->GetSystemBubble()->bubble_view()->GetViewByID(
           VIEW_ID_USER_VIEW_MEDIA_INDICATOR);
 
-  StatusAreaWidget* widget = system_tray->status_area_widget();
+  StatusAreaWidget* widget = StatusAreaWidgetTestHelper::GetStatusAreaWidget();
   EXPECT_TRUE(widget->GetRootView()->visible());
   views::View* tray_view =
       widget->GetRootView()->GetViewByID(VIEW_ID_MEDIA_TRAY_VIEW);