Support stacktrace and objecthistogram service commands

tests/standalone/vmservice/unknown_command_test.dart

+// Copyright (c) 2013, 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.
+
+library unknown_command_test;
+
+import 'test_helper.dart';
+import 'package:expect/expect.dart';
+
+class UnknownCommandTest extends VmServiceRequestHelper {
+  UnknownCommandTest(port) : super('http://127.0.0.1:$port/badcommand');
+
+  onRequestCompleted(Map reply) {
+    Expect.equals('error', reply['type']);
+  }
+}
+
+main() {
+  var process = new TestLauncher('unknown_command_script.dart');
+  process.launch().then((port) {
+    var test = new UnknownCommandTest(port);
+    test.makeRequest().then((_) {
+      process.requestExit();
+    });
+  });
+}