Optional binary payloads in VM service events.

runtime/bin/vmservice/observatory/test/echo_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:typed_data';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'test_helper.dart';
+
+var tests = [
+
+(Isolate isolate) =>
+  isolate.vm.get('_echo').then((result) {
+    expect(result['type'], equals("message"));
+    expect(result['id'], equals("_echo/root"));
+}),
+
+(Isolate isolate) =>
+  isolate.get('_echo').then((result) {
+    expect(result['type'], equals("message"));
+    expect(result['id'], equals("_echo/isolate"));
+}),
+
+(Isolate isolate) {
+  Completer completer = new Completer();
+  isolate.vm.events.stream.listen((ServiceEvent event) {
+    if (event.eventType == '_Echo') {
+      expect(event.data.lengthInBytes, equals(3));
+      expect(event.data.getUint8(0), equals(0));
+      expect(event.data.getUint8(1), equals(128));
+      expect(event.data.getUint8(2), equals(255));
+      completer.complete();
+    }
+  });
+  isolate.get('_echo/event');
+  return completer.future;
+},
+
+];
+
+main(args) => runIsolateTests(args, tests);