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

pkg/analyzer/lib/file_system/physical_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 physical_file_system;
 
 import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:analyzer/src/generated/java_io.dart';
@@ skipping 112 matching lines @@
     return isWithin(this.path, path);
   }
 
   @override
   Resource getChild(String relPath) {
     String canonicalPath = canonicalizePath(relPath);
     return PhysicalResourceProvider.INSTANCE.getResource(canonicalPath);
   }
 
   @override
+  _PhysicalFolder getChildAssumingFolder(String relPath) {
+    String canonicalPath = canonicalizePath(relPath);
+    io.Directory directory = new io.Directory(canonicalPath);
+    return new _PhysicalFolder(directory);
+  }
+
+  @override
   List<Resource> getChildren() {
     List<Resource> children = <Resource>[];
     io.Directory directory = _entry as io.Directory;
     List<io.FileSystemEntity> entries = directory.listSync(recursive: false);
     int numEntries = entries.length;
     for (int i = 0; i < numEntries; i++) {
       io.FileSystemEntity entity = entries[i];
       if (entity is io.Directory) {
         children.add(new _PhysicalFolder(entity));
       } else if (entity is io.File) {
@@ skipping 46 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }