Remove uses of the old plugin model from the analysis server

pkg/analysis_server/test/edit/fixes_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.
 
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
 import 'package:analysis_server/src/plugin/plugin_manager.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart' as plugin;
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:analyzer_plugin/protocol/protocol_generated.dart' as plugin;
 import 'package:analyzer_plugin/src/protocol/protocol_internal.dart' as plugin;
-import 'package:plugin/manager.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../analysis_abstract.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(FixesTest);
   });
 }
 
 @reflectiveTest
 class FixesTest extends AbstractAnalysisTest {
   @override
   void setUp() {
     super.setUp();
-    ExtensionManager manager = new ExtensionManager();
-    manager.processPlugins([server.serverPlugin]);
     handler = new EditDomainHandler(server);
   }
 
   test_fixUndefinedClass() async {
     createProject();
     addTestFile('''
 main() {
   Future<String> x = null;
 }
 ''');
@@ skipping 114 matching lines @@
     return await _getFixes(offset);
   }
 
   void _isSyntacticErrorWithSingleFix(AnalysisErrorFixes fixes) {
     AnalysisError error = fixes.error;
     expect(error.severity, AnalysisErrorSeverity.ERROR);
     expect(error.type, AnalysisErrorType.SYNTACTIC_ERROR);
     expect(fixes.fixes, hasLength(1));
   }
 }