refactor timing tests to not use the test framework

pkg/analysis_server/benchmark/perf/performance_tests.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.
 
 library server.performance;
 
 import 'dart:async';
+import 'dart:io';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../test/integration/integration_tests.dart';
 
 /**
  * Base class for analysis server performance tests.
  */
 abstract class AbstractAnalysisServerPerformanceTest
@@ skipping 42 matching lines @@
    */
   Future subscribeToStatusNotifications() {
     List<Future> futures = <Future>[];
     futures.add(sendServerSetSubscriptions([ServerService.STATUS]));
     return Future.wait(futures);
   }
 
   /**
    * After every test, the server is stopped.
    */
-  @override
-  Future tearDown() => shutdownIfNeeded();
+  Future shutdown() async => await shutdownIfNeeded();
 }
+
+class AbstractTimingTest extends AbstractAnalysisServerPerformanceTest {
+  Future init(String source) async {
+    await super.setUp();
+    sourceDirectory = new Directory(source);
+    return subscribeToStatusNotifications();
+  }
+}