Switch analysis_server to use 'package:test'.

pkg/analysis_server/benchmark/perf/memory_tests.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.
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 import '../../test/integration/integration_tests.dart';
 
 void printMemoryResults(String id, String description, List<int> sizes) {
   int minMemory = sizes.fold(sizes.first, min);
   int maxMemory = sizes.fold(sizes.first, max);
   String now = new DateTime.now().toUtc().toIso8601String();
   print('$now ========== $id');
   print('memory: $sizes');
   print('min_memory: $minMemory');
@@ skipping 99 matching lines @@
       // Set roots and analyze.
       await test.sendAnalysisSetAnalysisRoots(roots, []);
       await test.analysisFinished;
       sizes.add(test.getMemoryUsage());
       // Stop the server.
       await test.shutdown();
     }
     return sizes;
   }
 }