Provide an API to dart:developer to control the web server hosting the Service Protocol

runtime/observatory/tests/service/developer_server_control_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.
+// VMOptions=--error_on_bad_type --error_on_bad_override
+
+import 'dart:async';
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'test_helper.dart';
+
+Future<Null> testeeBefore() async {
+  print('testee before');
+  print(await Service.getInfo());
+  // Start the web server.
+  ServiceProtocolInfo info = await Service.controlWebServer(enable: true);
+  print(info);
+}
+
+var tests = [
+(Isolate isolate) async {
+  await isolate.reload();
+  // Just getting here means that the testee enabled the service protocol
+  // web server.
+  expect(true, true);

[rmacnak, 2016/10/20 17:12:31]

true, isTrue

[Cutch, 2016/10/20 23:31:51]

expect(true, true) is equivalent

+}
+];
+
+main(args) => runIsolateTests(args,
+                              tests,
+                              testeeBefore: testeeBefore,
+                              // the testee is responsible for starting the
+                              // web server.
+                              testeeControlsServer: true);