Refactor service tests in preparation of running on sky_shell

runtime/observatory/tests/service/vm_timeline_flags_test.dart

 // Copyright (c) 2016, 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:developer';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
-
+import 'service_test_common.dart';
 import 'test_helper.dart';
 
 primeDartTimeline() {
   while (true) {
     Timeline.startSync('apple');
     Timeline.finishSync();
     debugger();
   }
 }
 
@@ skipping 85 matching lines @@
     // Confirm that zero non-Dart events are added.
     expect(
         filterEvents(result['traceEvents'], isNotDartAndMetaData).length,
         equals(0));
   },
 ];
 
 main(args) async => runIsolateTests(args,
                                     tests,
                                     testeeConcurrent: primeDartTimeline);