Fix the async compiler, and pub's async compiler test.

pkg/scheduled_test/lib/src/descriptor/directory_descriptor.dart

 // Copyright (c) 2013, 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 descriptor.directory;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 13 matching lines @@
       : super(name),
         contents = contents.toList();
 
   /// Creates a directory descriptor named [name] based on a directory on the
   /// physical directory at [path].
   ///
   /// Note that reading from the filesystem isn't scheduled; it occurs as soon
   /// as this descriptor is constructed.
   DirectoryDescriptor.fromFilesystem(String name, String path)
       : this(name, new Directory(path).listSync().map((entity) {
+          // Ignore hidden files.
+          if (p.basename(entity.path).startsWith(".")) return null;
+
           if (entity is Directory) {
             return new DirectoryDescriptor.fromFilesystem(
                 p.basename(entity.path), entity.path);
           } else if (entity is File) {
             return new FileDescriptor.binary(
                 p.basename(entity.path), entity.readAsBytesSync());
           }
           // Ignore broken symlinks.
-        }));
+        }).where((path) => path != null));
 
   Future create([String parent]) => schedule(() {
     if (parent == null) parent = defaultRoot;
     var fullPath = p.join(parent, name);
     return Chain.track(new Directory(fullPath).create(recursive: true))
         .then((_) {
       return Future.wait(
           contents.map((entry) => entry.create(fullPath)).toList());
     });
   }, 'creating directory:\n${describe()}');
@@ skipping 90 matching lines @@
 
   _DirectoryValidationError(Iterable errors)
       : errors = errors.map((e) => e.toString()).toList();
 
   String toString() {
     if (errors.length == 1) return errors.single;
     return errors.map((e) => prefixLines(e, prefix: '  ', firstPrefix: '* '))
         .join('\n');
   }
 }