Add flag for face message defer logic update

When this flag is enabled, the face message
defer logic will only analyze the last n frames
received by the faceManager rather than analyzing
all the frames to determine whether to show a face
help message on face TIMEOUT

Flag: com.android.systemui.face_message_defer_update
Bug: 351863611
Test: builds
Change-Id: Ifcd37e669ed65128a99cdf9d2d55f17b6bf34591
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index 7c0db8d..47c0ca8 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -1346,3 +1346,14 @@
     purpose: PURPOSE_BUGFIX
   }
 }
+
+flag {
+    name: "face_message_defer_update"
+    namespace: "systemui"
+    description: "Only analyze the last n frames when determining whether to defer a face auth help message like low light"
+    bug: "351863611"
+    metadata {
+      purpose: PURPOSE_BUGFIX
+    }
+}
+