Clean-up imports

pkg/analyzer/test/src/task/strong/strong_test_helper.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.
 
 // TODO(jmesserly): this file needs to be refactored, it's a port from
 // package:dev_compiler's tests
 library analyzer.test.src.task.strong.strong_test_helper;
 
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/context/context.dart' show SdkAnalysisContext;
-import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/type_system.dart';
 import 'package:analyzer/src/task/strong/checker.dart';
 import 'package:logging/logging.dart';
 import 'package:source_span/source_span.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 490 matching lines @@
   UriKind get uriKind => UriKind.DART_URI;
 
   bool exists() => true;
 
   Source resolveRelative(Uri relativeUri) =>
       throw new UnsupportedError('not expecting relative urls in dart: mocks');
 
   Uri resolveRelativeUri(Uri relativeUri) =>
       throw new UnsupportedError('not expecting relative urls in dart: mocks');
 }