Add feature flag for media action button updates

Bug: 360196209
Flag: com.android.systemui.media_controls_button_media3

Change-Id: I31f135b66af0f250a95fa16b98749d92aefcd3be
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index cdbac33..9d10397 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -1035,6 +1035,13 @@
 }
 
 flag {
+  name: "media_controls_button_media3"
+  namespace: "systemui"
+  description: "Enable media action buttons updates using media3"
+  bug: "360196209"
+}
+
+flag {
   namespace: "systemui"
   name: "enable_view_capture_tracing"
   description: "Enables view capture tracing in System UI."