Mark generated abstract class as Experimental
diff --git a/compiler/src/testNano/golden/TestService.java.txt b/compiler/src/testNano/golden/TestService.java.txt
index ccd028e..1f2c91c 100644
--- a/compiler/src/testNano/golden/TestService.java.txt
+++ b/compiler/src/testNano/golden/TestService.java.txt
@@ -181,6 +181,7 @@
         io.grpc.stub.StreamObserver<io.grpc.testing.integration.nano.Test.StreamingOutputCallResponse> responseObserver);
   }
 
+  @io.grpc.ExperimentalApi
   public static abstract class AbstractTestService implements TestService, io.grpc.BindableService {
 
     @java.lang.Override