Remove the old task model

pkg/analyzer/test/src/task/general_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 test.src.task.general_test;
 
-import 'package:analyzer/src/generated/engine.dart'
-    hide AnalysisTask, GetContentTask;
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/general.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:typed_mock/typed_mock.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/test_support.dart';
 import '../../reflective_tests.dart';
 import '../../utils.dart';
@@ skipping 58 matching lines @@
     expect(task.caughtException, isNull);
     expect(task.outputs, hasLength(2));
     expect(task.outputs[CONTENT], '');
     expect(task.outputs[MODIFICATION_TIME], -1);
   }
 }
 
 class _MockContext extends TypedMock implements AnalysisContext {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }