Big merge from experimental to bleeding edge.

utils/pub/package.dart

 // Copyright (c) 2012, 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 package;
 
+import 'dart:async';
 import 'io.dart';
 import 'pubspec.dart';
 import 'source.dart';
 import 'source_registry.dart';
 import 'version.dart';
 
 /// A named, versioned, unit of code and resource reuse.
 class Package {
   /// Loads the package whose root directory is [packageDir]. [name] is the
   /// expected name of that package (e.g. the name given in the dependency), or
   /// null if the package being loaded is the entrypoint package.
   static Future<Package> load(String name, String packageDir,
       SourceRegistry sources) {
     var pubspecPath = join(packageDir, 'pubspec.yaml');
 
-    return fileExists(pubspecPath).chain((exists) {
+    return fileExists(pubspecPath).then((exists) {
       if (!exists) throw new PubspecNotFoundException(name);
       return readTextFile(pubspecPath);
-    }).transform((contents) {
+    }).then((contents) {
       try {
         var pubspec = new Pubspec.parse(contents, sources);
 
         if (pubspec.name == null) throw new PubspecHasNoNameException(name);
         if (name != null && pubspec.name != name) {
           throw new PubspecNameMismatchException(name, pubspec.name);
         }
         return new Package._(packageDir, pubspec);
       } on FormatException catch (ex) {
         throw 'Could not parse $pubspecPath:\n${ex.message}';
@@ skipping 143 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }