Add a flag to a previous API change.

This was changed recently b/216813597 and at that point it should have
been behind a flag.

Bug: 304478551
Test: it builds fine?
Change-Id: I21912cc463632ec867b50c7100b6a50222d9f771
diff --git a/graphics/java/Android.bp b/graphics/java/Android.bp
index 63d1f6d..db37a387 100644
--- a/graphics/java/Android.bp
+++ b/graphics/java/Android.bp
@@ -7,6 +7,12 @@
     default_applicable_licenses: ["frameworks_base_license"],
 }
 
+aconfig_declarations {
+    name: "framework_graphics_flags",
+    package: "com.android.graphics.flags",
+    srcs: ["android/framework_graphics.aconfig"],
+}
+
 filegroup {
     name: "framework-graphics-nonupdatable-sources",
     srcs: [