pkg/unittest: fix analyzer errors

test/util/parse_annotations_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.
 
 import 'dart:io';
 
+import 'package:analyzer/src/generated/ast.dart';
 import 'package:path/path.dart' as p;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/src/util/dart.dart';
 
 String _sandbox;
 String _path;
 
 void main() {
   setUp(() {
     _sandbox = Directory.systemTemp.createTempSync('unittest_').path;
@@ skipping 152 matching lines @@
 
       var annotations = parseAnnotations(_path);
       expect(annotations, hasLength(2));
       expect(annotations[0].name.name, equals('Annotation1'));
       expect(annotations[0].arguments.arguments, isEmpty);
       expect(annotations[1].name.name, equals('Annotation2'));
       expect(annotations[1].arguments.arguments, isEmpty);
     });
   });
 }