Add flag for NotificationLockscreenUserManagerImpl refactor

Change-Id: If67baa66a392cb7833ec8a936ee5bbda07d4a666
Test: build
Bug: 286230167
Bug: 301955929
diff --git a/packages/SystemUI/src/com/android/systemui/flags/Flags.kt b/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
index 467e84d..ecad9d7 100644
--- a/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
+++ b/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
@@ -124,6 +124,11 @@
     val NOTIFICATION_GROUP_EXPANSION_CHANGE =
             unreleasedFlag("notification_group_expansion_change")
 
+    // TODO(b/301955929)
+    @JvmField
+    val NOTIF_LS_BACKGROUND_THREAD =
+            unreleasedFlag("notification_lockscreen_mgr_bg_thread")
+
     // 200 - keyguard/lockscreen
     // ** Flag retired **
     // public static final BooleanFlag KEYGUARD_LAYOUT =