Add Iterable.fold (and Stream.fold) which replace `reduce`.

utils/pub/io.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.
 
 /// Helper functionality to make working with IO easier.
 library io;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 310 matching lines @@
 Future<bool> confirm(String message) {
   log.fine('Showing confirm message: $message');
   stdoutSink.add("$message (y/n)? ".codeUnits);
   return streamFirst(stdinLines)
       .then((line) => new RegExp(r"^[yY]").hasMatch(line));
 }
 
 /// Reads and discards all output from [stream]. Returns a [Future] that
 /// completes when the stream is closed.
 Future drainStream(Stream stream) {
-  return stream.reduce(null, (x, y) {});
+  return stream.fold(null, (x, y) {});
 }
 
 /// Returns a [EventSink] that pipes all data to [consumer] and a [Future] that
 /// will succeed when [EventSink] is closed or fail with any errors that occur
 /// while writing.
 Pair<EventSink, Future> consumerToSink(StreamConsumer consumer) {
   var controller = new StreamController();
   var done = controller.stream.pipe(consumer);
   return new Pair<EventSink, Future>(controller.sink, done);
 }
@@ skipping 392 matching lines @@
   const PubProcessResult(this.stdout, this.stderr, this.exitCode);
 
   bool get success => exitCode == 0;
 }
 
 /// Gets a [Uri] for [uri], which can either already be one, or be a [String].
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return Uri.parse(uri);
 }