Dart: Futures -> Callbacks.

mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart

Index: mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart
diff --git a/mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart b/mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart
index b82ade9fbaa77031298264b073fbcb352858d0a9..cfa6d9d557cb56db2bdb9abf7181091a9359f732 100644
--- a/mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart
+++ b/mojo/dart/apptests/test_apps/pingpong_target/lib/main.dart
@@ -33,13 +33,12 @@ class PingPongServiceImpl implements PingPongService {
   void ping(int pingValue) => _pingPongClient.pong(pingValue + 1);
 
   // These methods are unimplemented; they merely throw on invocation.
-  dynamic pingTargetUrl(String url, int count, [Function responseFactory]) =>
+  void pingTargetUrl(String url, int count, void callback(bool ok)) =>
       throw "Unimplemented";
-  dynamic pingTargetService(PingPongServiceInterface service, int count,
-      [Function responseFactory]) =>
+  void pingTargetService(PingPongServiceInterface service, int count,
+      void callback(bool ok)) =>
       throw "Unimplemented";
-  dynamic getPingPongServiceDelayed(PingPongServiceInterfaceRequest service,
-      [Function responseFactory]) =>
+  void getPingPongServiceDelayed(PingPongServiceInterfaceRequest service) =>
       throw "Unimplemented";
 
   void getPingPongService(PingPongServiceInterfaceRequest service) {