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

pkg/analyzer/lib/file_system/file_system.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 file_system;
 
 import 'dart:async';
 
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
@@ skipping 59 matching lines @@
    * Return an existing child [Resource] with the given [relPath].
    * Return a not existing [File] if no such child exist.
    */
   Resource getChild(String relPath);
 
   /**
    * Return a list of existing direct children [Resource]s (folders and files)
    * in this folder, in no particular order.
    */
   List<Resource> getChildren();
+
+  /**
+   * Return a [Folder] representing a child [Resource] with the given
+   * [relPath].  This call does not check whether a folder with the given name
+   * exists on the filesystem--client must call the [Folder]'s `exists` getter
+   * to determine whether the folder actually exists.
+   */
+  Folder getChildAssumingFolder(String relPath);
 }
 
 
 /**
  * The abstract class [Resource] is an abstraction of file or folder.
  */
 abstract class Resource {
   /**
    * Return `true` if this resource exists.
    */
@@ skipping 80 matching lines @@
   Uri restoreAbsolute(Source source) => source.uri;
 
   /**
    * Return `true` if the given URI is a `file` URI.
    *
    * @param uri the URI being tested
    * @return `true` if the given URI is a `file` URI
    */
   static bool _isFileUri(Uri uri) => uri.scheme == _FILE_SCHEME;
 }