Adds aconfig flag for CallStyle notif. callback API

Bug: 305095040
Test: m -j
Change-Id: I068ab9dd23c609178f3395d262461f8b269353e7
diff --git a/core/java/android/service/notification/flags.aconfig b/core/java/android/service/notification/flags.aconfig
index a2ade6a..3008b8d 100644
--- a/core/java/android/service/notification/flags.aconfig
+++ b/core/java/android/service/notification/flags.aconfig
@@ -21,3 +21,11 @@
   description: "This flag controls the redacting of sensitive notifications from untrusted NotificationListenerServices"
   bug: "306271190"
 }
+
+flag {
+  name: "callstyle_callback_api"
+  namespace: "systemui"
+  description: "Guards the new CallStyleNotificationEventsCallback"
+  bug: "305095040"
+  is_fixed_read_only: true
+}
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