[flexiglass] Creates top-level aconfig flag.

Bug: 283121968
Change-Id: Id887212eece8535f08006ae1ad089eaca20ccb33
Test: N/A
Flag: type:ACONFIG scene_container state:DEVELOPMENT
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index 2509cfd..211af90 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -29,3 +29,10 @@
         "Notification Manager Service"
     bug: "299448097"
 }
+
+flag {
+    name: "scene_container"
+    namespace: "systemui"
+    description: "Enables the scene container framework go/flexiglass."
+    bug: "283121968"
+}