pkg/analysis_server: fixes for unittest deprecations

pkg/analysis_server/test/domain_server_test.dart

 // Copyright (c) 2014, 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 test.domain.server;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/domain_server.dart';
 import 'package:analysis_server/src/protocol.dart';
-import 'package:unittest/matcher.dart';
 import 'package:unittest/unittest.dart';
 
 import 'mocks.dart';
 
 main() {
   group('ServerDomainHandler', () {
 //    test('createContext', ServerDomainHandlerTest.createContext);
 //    test('deleteContext_alreadyDeleted', ServerDomainHandlerTest.deleteContext_alreadyDeleted);
     test('deleteContext_doesNotExist', ServerDomainHandlerTest.deleteContext_doesNotExist);
 //    test('deleteContext_existing', ServerDomainHandlerTest.deleteContext_existing);
@@ skipping 84 matching lines @@
     Response response = handler.handleRequest(versionRequest);
     expect(response.toJson(), equals({
       Response.ID: '0',
       Response.ERROR: null,
       Response.RESULT: {
         ServerDomainHandler.VERSION_RESULT: '0.0.1'
       }
     }));
   }
 }