Refactor Future constructors.

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:pathos/path.dart' as path;
@@ skipping 28 matching lines @@
       'validating directory:\n${describe()}');
 
   Future validateNow([String parent]) {
     if (parent == null) parent = defaultRoot;
     var fullPath = path.join(parent, name);
     if (!new Directory(fullPath).existsSync()) {
       throw "Directory not found: '$fullPath'.";
     }
 
     return Future.wait(contents.map((entry) {
-      return new Future.of(() => entry.validateNow(fullPath))
+      return new Future.sync(() => entry.validateNow(fullPath))
           .then((_) => null)
           .catchError((e) => e);
     })).then((results) {
       var errors = results.where((e) => e != null);
       if (errors.isEmpty) return;
       throw _DirectoryValidationError.merge(errors);
     });
   }
 
   Stream<List<int>> load(String pathToLoad) {
-    return futureStream(new Future.immediate(null).then((_) {
+    return futureStream(new Future.value().then((_) {
       if (_path.isAbsolute(pathToLoad)) {
         throw "Can't load absolute path '$pathToLoad'.";
       }
 
       var split = _path.split(_path.normalize(pathToLoad));
       if (split.isEmpty || split.first == '.' || split.first == '..') {
         throw "Can't load '$pathToLoad' from within '$name'.";
       }
 
       var matchingEntries = contents.where((entry) =>
@@ skipping 50 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');
   }
 }