do not expose Service

Author: pongad

google-cloud-examples/src/main/java/com/google/cloud/examples/pubsub/snippets/CreateSubscriptionAndPullMessages.java

@@ -54,9 +54,9 @@ public ListenableFuture<MessageReceiver.AckReply> receiveMessage(PubsubMessage m
     try {
       subscriber = Subscriber.Builder.newBuilder(subscription, receiver).build();
       subscriber.addListener(
-          new Service.Listener() {
+          new Subscriber.SubscriberListener() {
             @Override
-            public void failed(Service.State from, Throwable failure) {
+            public void failed(Subscriber.State from, Throwable failure) {
               System.err.println(failure);
             }
           },