Dart: Removes all but native calls and the handle watcher from the snapshot.

services/dart/test/pingpong_target/main.dart

Index: services/dart/test/pingpong_target/main.dart
diff --git a/services/dart/test/pingpong_target/main.dart b/services/dart/test/pingpong_target/main.dart
index 36f8a26a65b111ec1fc70b4251236def942c89a9..bf7fb78033640a572130835ad6d1761df6084346 100644
--- a/services/dart/test/pingpong_target/main.dart
+++ b/services/dart/test/pingpong_target/main.dart
@@ -3,9 +3,10 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:mojo.application';
-import 'dart:mojo.bindings';
-import 'dart:mojo.core';
+
+import 'package:mojo/public/dart/application.dart';
+import 'package:mojo/public/dart/bindings.dart';
+import 'package:mojo/public/dart/core.dart';
 
 import 'package:services/dart/test/pingpong_service.mojom.dart';