Refactor service tests in preparation of running on sky_shell

runtime/observatory/tests/service/developer_extension_test.dart

 // Copyright (c) 2015, 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:convert';
 import 'dart:developer';
 import 'package:observatory/service_io.dart';
 import 'package:observatory/cpu_profile.dart';
 import 'package:unittest/unittest.dart';
-
+import 'service_test_common.dart';
 import 'test_helper.dart';
 
 Future<ServiceExtensionResponse> Handler(String method,
                                          Map paremeters) {
   print('Invoked extension: $method');
   switch (method) {
     case 'ext..delay':
       Completer c = new Completer();
       new Timer(new Duration(seconds: 1), () {
         c.complete(new ServiceExtensionResponse.result(JSON.encode({
@@ skipping 124 matching lines @@
       expect(e.message, stringContainsInOrder([
           'Error in extension `ext..languageError`:',
           'developer_extension_test.dart',
           'semicolon expected']));
     }
   },
 ];
 
 main(args) async => runIsolateTests(args, tests, testeeConcurrent:test,
                                     trace_compiler: true);