Clean up after some recent code changes

pkg/analyzer_plugin/test/plugin/mocks.dart

 // Copyright (c) 2017, 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:collection';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 101 matching lines @@
     }
     Completer<Response> completer = completers.remove(response.id);
     completer.complete(response);
   }
 }
 
 /**
  * A concrete implementation of a server plugin that is suitable for testing.
  */
 class MockServerPlugin extends ServerPlugin {
-  MockChannel mockChannel = new MockChannel();
-
   MockServerPlugin(ResourceProvider resourceProvider) : super(resourceProvider);
 
   @override
-  PluginCommunicationChannel get channel => mockChannel;
-
-  @override
   List<String> get fileGlobsToAnalyze => <String>['*.dart'];
 
   @override
   String get name => 'Test Plugin';
 
   @override
   String get version => '0.1.0';
 
   @override
   AnalysisDriverGeneric createAnalysisDriver(ContextRoot contextRoot) {
@@ skipping 28 matching lines @@
 
   @override
   Uri get uri => Uri.parse('package:test/test.dart');
 
   @override
   UriKind get uriKind => UriKind.PACKAGE_URI;
 
   @override
   bool exists() => true;
 }