Introduce window container to be used by lock screen app windows

ash/tray_action/tray_action.cc

Index: ash/tray_action/tray_action.cc
diff --git a/ash/tray_action/tray_action.cc b/ash/tray_action/tray_action.cc
index 6437c61f17db8de21b6b553e56acde0e8889609c..4e0bdd83b2fda3c75ae07651b2a1d16118d26010 100644
--- a/ash/tray_action/tray_action.cc
+++ b/ash/tray_action/tray_action.cc
@@ -29,12 +29,16 @@ void TrayAction::BindRequest(mojom::TrayActionRequest request) {
   bindings_.AddBinding(this, std::move(request));
 }
 
-mojom::TrayActionState TrayAction::GetLockScreenNoteState() {
+mojom::TrayActionState TrayAction::GetLockScreenNoteState() const {
   if (!tray_action_client_)
     return mojom::TrayActionState::kNotAvailable;
   return lock_screen_note_state_;
 }
 
+bool TrayAction::IsLockScreenNoteActive() const {
+  return GetLockScreenNoteState() == mojom::TrayActionState::kActive;
+}
+
 void TrayAction::SetClient(mojom::TrayActionClientPtr tray_action_client,
                            mojom::TrayActionState lock_screen_note_state) {
   mojom::TrayActionState old_lock_screen_note_state = GetLockScreenNoteState();