Simplify ping and pong

The simple demo apps grew to the point where they were no longer simple
and easy to understand since I was using them to test out timing reports
and accidentally committed the changes.  Restore the simplicity.

Change-Id: I453fa0351247c4549098660cd21191659269f515
diff --git a/aos/events/pong_lib.cc b/aos/events/pong_lib.cc
index 5ff38b9..9d7731d 100644
--- a/aos/events/pong_lib.cc
+++ b/aos/events/pong_lib.cc
@@ -1,8 +1,8 @@
 #include "aos/events/pong_lib.h"
 
 #include "aos/events/event_loop.h"
-#include "aos/events/pong_generated.h"
 #include "aos/events/ping_generated.h"
+#include "aos/events/pong_generated.h"
 #include "glog/logging.h"
 
 namespace aos {
@@ -11,11 +11,12 @@
     : event_loop_(event_loop),
       sender_(event_loop_->MakeSender<examples::Pong>("/test")) {
   event_loop_->MakeWatcher("/test", [this](const examples::Ping &ping) {
-    aos::Sender<examples::Pong>::Builder msg = sender_.MakeBuilder();
-    examples::Pong::Builder builder = msg.MakeBuilder<examples::Pong>();
-    builder.add_value(ping.value());
-    builder.add_initial_send_time(ping.send_time());
-    CHECK(msg.Send(builder.Finish()));
+    aos::Sender<examples::Pong>::Builder builder = sender_.MakeBuilder();
+    examples::Pong::Builder pong_builder =
+        builder.MakeBuilder<examples::Pong>();
+    pong_builder.add_value(ping.value());
+    pong_builder.add_initial_send_time(ping.send_time());
+    CHECK(builder.Send(pong_builder.Finish()));
   });
 
   event_loop_->SetRuntimeRealtimePriority(5);