Fix two analyzer warnings.

pkg/analyzer/test/generated/gn_test.dart

 // Copyright (c) 2017, 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.generated.gn_test;
 
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/gn.dart';
-import 'package:analyzer/src/generated/source.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(GnWorkspaceTest);
   });
 }
 
 @reflectiveTest
@@ skipping 53 matching lines @@
 }
 
 class _BaseTest {
   final MemoryResourceProvider provider = new MemoryResourceProvider();
 
   /**
    * Return the [provider] specific path for the given Posix [path].
    */
   String _p(String path) => provider.convertPath(path);
 }