Revert breaking change

pkg/analyzer/test/src/context/context_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.src.context.context_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/cancelable_future.dart';
@@ skipping 26 matching lines @@
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/generated/testing/ast_factory.dart';
 import 'package:analyzer/src/generated/testing/element_factory.dart';
 import 'package:analyzer/src/generated/testing/test_type_provider.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:analyzer/src/plugin/engine_plugin.dart';
-import 'package:plugin/manager.dart';
+import 'package:analyzer/src/plugin/plugin_impl.dart';
 import 'package:unittest/unittest.dart';
 import 'package:watcher/src/utils.dart';
 
 import '../../generated/engine_test.dart';
 import '../../generated/test_support.dart';
 import '../../reflective_tests.dart';
 
 main() {
   groupSep = ' | ';
   runReflectiveTests(AnalysisContextImplTest);
@@ skipping 2403 matching lines @@
       : super(name, UriKind.FILE_URI);
 
   @override
   TimestampedData<String> get contents {
     throw 'Read error';
   }
 
   @override
   bool exists() => true;
 }