Switch analysis_server to use 'package:test'.

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 'package:test/test.dart';
 
 import '../../test/integration/integration_tests.dart';
 
 /**
  * Base class for analysis server performance tests.
  */
 abstract class AbstractAnalysisServerPerformanceTest
     extends AbstractAnalysisServerIntegrationTest {
   /**
    * Stopwatch for timing results;
@@ skipping 47 matching lines @@
   }
 }
 
 class AbstractTimingTest extends AbstractAnalysisServerPerformanceTest {
   Future init(String source) async {
     await super.setUp();
     sourceDirectory = new Directory(source);
     return subscribeToStatusNotifications();
   }
 }