Don't do folder existence checks when parsing pub list results.

pkg/analyzer/test/file_system/memory_file_system_test.dart

 // Copyright (c) 2014, 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.memory_file_system;
 
 import 'dart:async';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 import 'package:watcher/watcher.dart';
 
 
 var _isFile = new isInstanceOf<File>();
+var _isFileSystemException = new isInstanceOf<FileSystemException>();
 var _isFolder = new isInstanceOf<Folder>();
-var _isFileSystemException = new isInstanceOf<FileSystemException>();
 
 
 main() {
   groupSep = ' | ';
 
   group('MemoryResourceProvider', () {
     MemoryResourceProvider provider;
 
     setUp(() {
       provider = new MemoryResourceProvider();
@@ skipping 339 matching lines @@
         });
 
         test('folder', () {
           provider.newFolder('/foo/bar/baz');
           Folder child = folder.getChild('baz');
           expect(child, isNotNull);
           expect(child.exists, isTrue);
         });
       });
 
+      group('getChildAssumingFolder', () {
+        test('does not exist', () {
+          Folder child = folder.getChildAssumingFolder('foldername');
+          expect(child, isNotNull);
+          expect(child.exists, isFalse);
+        });
+
+        test('file', () {
+          provider.newFile('/foo/bar/foldername', 'content');
+          Folder child = folder.getChildAssumingFolder('foldername');
+          expect(child, isNotNull);
+          expect(child.exists, isFalse);
+        });
+
+        test('folder', () {
+          provider.newFolder('/foo/bar/foldername');
+          Folder child = folder.getChildAssumingFolder('foldername');
+          expect(child, isNotNull);
+          expect(child.exists, isTrue);
+        });
+      });
+
       test('getChildren', () {
         provider.newFile('/foo/bar/a.txt', 'aaa');
         provider.newFolder('/foo/bar/bFolder');
         provider.newFile('/foo/bar/c.txt', 'ccc');
         // prepare 3 children
         List<Resource> children = folder.getChildren();
         expect(children, hasLength(3));
         children.sort((a, b) => a.shortName.compareTo(b.shortName));
         // check that each child exists
         children.forEach((child) {
@@ skipping 137 matching lines @@
 
         test('resolveRelative', () {
           Uri relative =
               source.resolveRelativeUri(new Uri.file('bar/baz.dart'));
           expect(relative.path, '/foo/bar/baz.dart');
         });
       });
     });
   });
 }