Adds ash_mus_unittests to FYI bot

ash/wm/overview/window_selector_unittest.cc

Index: ash/wm/overview/window_selector_unittest.cc
diff --git a/ash/wm/overview/window_selector_unittest.cc b/ash/wm/overview/window_selector_unittest.cc
index c90f08c81e556420b8bd98a9d1cb5a8e271f49e8..b65242757392e41d2d0bbb4ef6b2db0ffdc9a56a 100644
--- a/ash/wm/overview/window_selector_unittest.cc
+++ b/ash/wm/overview/window_selector_unittest.cc
@@ -940,7 +940,8 @@ TEST_F(WindowSelectorTest, SelectingHidesAppList) {
   // The tested behavior relies on the app list presenter delegate.
   test::TestAppListViewPresenterImpl app_list_presenter_impl;
 
-  app_list_presenter_impl.Show(display_manager()->first_display_id());
+  app_list_presenter_impl.Show(
+      display::Screen::GetScreen()->GetPrimaryDisplay().id());
   EXPECT_TRUE(app_list_presenter_impl.IsVisible());
 
   ToggleOverview();