Break up another large file

pkg/analyzer/test/src/task/dart_work_manager_test.dart

 // Copyright (c) 2015, 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 analyzer.test.src.task.dart_work_manager_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/error/error.dart' show AnalysisError;
 import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart' show ScannerErrorCode;
 import 'package:analyzer/src/generated/engine.dart'
     show
         AnalysisErrorInfoImpl,
         CacheState,
         ChangeNoticeImpl,
         InternalAnalysisContext;
-import 'package:analyzer/src/generated/error.dart' show AnalysisError;
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/testing/ast_factory.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/dart_work_manager.dart';
 import 'package:analyzer/task/dart.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:typed_mock/typed_mock.dart';
@@ skipping 826 matching lines @@
 class _SourceFactoryMock extends TypedMock implements SourceFactory {}
 
 class _SourceMock extends TypedMock implements Source {
   final String shortName;
   _SourceMock(this.shortName);
   @override
   String get fullName => '/' + shortName;
   @override
   String toString() => fullName;
 }