pkg/analysis_server: fixes for unittest deprecations

pkg/analysis_server/test/mocks.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 mocks;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/channel.dart';
 import 'package:analysis_server/src/protocol.dart';
-import 'package:unittest/matcher.dart';
+import 'package:matcher/matcher.dart';
 
 /**
  * Answer the absolute path the the SDK relative to the currently running
  * script or throw an exception if it cannot be found.
  */
 String get sdkPath {
   Uri sdkUri = Platform.script.resolve('../../../sdk/');
 
   // Verify the directory exists
   Directory sdkDir = new Directory.fromUri(sdkUri);
@@ skipping 82 matching lines @@
     responsesReceived.add(response);
     // Wrap send response in future to simulate websocket
     new Future(() => responseController.add(response));
   }
 
   void expectMsgCount({responseCount: 0, notificationCount: 0}) {
     expect(responsesReceived, hasLength(responseCount));
     expect(notificationsReceived, hasLength(notificationCount));
   }
 }