xds: Fixed to pretty-print XdsClusterResource with RoundRobin

Author: vinodhabib

xds/src/main/java/io/grpc/xds/MessagePrinter.java

@@ -33,6 +33,7 @@
 import io.envoyproxy.envoy.extensions.filters.http.rbac.v3.RBACPerRoute;
 import io.envoyproxy.envoy.extensions.filters.http.router.v3.Router;
 import io.envoyproxy.envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager;
+import io.envoyproxy.envoy.extensions.load_balancing_policies.round_robin.v3.RoundRobin;
 import io.envoyproxy.envoy.extensions.load_balancing_policies.wrr_locality.v3.WrrLocality;
 import io.envoyproxy.envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext;
 import io.envoyproxy.envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext;
@@ -69,7 +70,8 @@ private static JsonFormat.Printer newPrinter() {
               .add(ClusterConfig.getDescriptor())
               .add(ClusterLoadAssignment.getDescriptor())
               .add(WrrLocality.getDescriptor())
-              .add(TypedStruct.getDescriptor());
+              .add(TypedStruct.getDescriptor())
+              .add(RoundRobin.getDescriptor());
       try {
         @SuppressWarnings("unchecked")
         Class<? extends Message> routeLookupClusterSpecifierClass =