SF: add a server writable flag (non boot stable)

Bug: 297389311
Test: presubmit
Change-Id: I35cd5b7dd6160bcc45873eafae35c7497539fe56
diff --git a/services/surfaceflinger/surfaceflinger_flags.aconfig b/services/surfaceflinger/surfaceflinger_flags.aconfig
index f47ed45..6519d3a 100644
--- a/services/surfaceflinger/surfaceflinger_flags.aconfig
+++ b/services/surfaceflinger/surfaceflinger_flags.aconfig
@@ -15,3 +15,10 @@
   bug: "278199093"
   is_fixed_read_only: true
 }
+
+flag{
+  name: "late_boot_misc2"
+  namespace: "core_graphics"
+  description: "This flag controls minor miscellaneous SurfaceFlinger changes. Cannot be read before boot finished!"
+  bug: "297389311"
+}