Add java_defaults for @FlaggedApi handling

This CL is a preparation to ignore @FlaggedApi API in udc mainline
branch

Bug: 299411828
Test: TH
Change-Id: If3217916b2c37ebaa7b48d8387c69cb078af9550
diff --git a/framework/Android.bp b/framework/Android.bp
index e577e6d..794e1db 100644
--- a/framework/Android.bp
+++ b/framework/Android.bp
@@ -19,6 +19,15 @@
     default_applicable_licenses: ["Android-Apache-2.0"],
 }
 
+// In the branch which does not support FlaggedAPI, use this default to ignore the annotated APIs.
+java_defaults {
+    name: "FlaggedApiDefaults",
+}
+
+// The above variables may have different values
+// depending on the branch, and this comment helps
+// separate them from the rest of the file to avoid merge conflicts
+
 filegroup {
     name: "framework-connectivity-internal-sources",
     srcs: [
@@ -152,6 +161,7 @@
     defaults: [
         "framework-connectivity-defaults",
         "CronetJavaDefaults",
+        "FlaggedApiDefaults",
     ],
     installable: true,
     jarjar_rules: ":framework-connectivity-jarjar-rules",