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

tests/lib/async/stream_controller_async_test.dart

 // Copyright (c) 2011, 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.
 
 // Test the basic StreamController and StreamController.singleSubscription.
 library stream_controller_async_test;
 
 import 'dart:async';
 import 'dart:isolate';
 import '../../../pkg/unittest/lib/unittest.dart';
 import 'event_helper.dart';
 
 testController() {
-  // Test reduce
-  test("StreamController.reduce", () {
+  // Test fold
+  test("StreamController.fold", () {
     StreamController c = new StreamController.broadcast();
     Stream stream = c.stream;
-    stream.reduce(0, (a,b) => a + b)
+    stream.fold(0, (a,b) => a + b)
      .then(expectAsync1((int v) {
         Expect.equals(42, v);
     }));
     c.add(10);
     c.add(32);
     c.close();
   });
 
-  test("StreamController.reduce throws", () {
+  test("StreamController.fold throws", () {
     StreamController c = new StreamController.broadcast();
     Stream stream = c.stream;
-    stream.reduce(0, (a,b) { throw "Fnyf!"; })
+    stream.fold(0, (a,b) { throw "Fnyf!"; })
      .catchError(expectAsync1((e) { Expect.equals("Fnyf!", e.error); }));
     c.add(42);
   });
 
   test("StreamController.pipeInto", () {
     StreamController c = new StreamController.broadcast();
     var list = <int>[];
     Stream stream = c.stream;
     stream.pipeInto(new CollectionSink<int>(list))
      .whenComplete(expectAsync0(() {
         Expect.listEquals(<int>[1,2,9,3,9], list);
       }));
     c.add(1);
     c.add(2);
     c.add(9);
     c.add(3);
     c.add(9);
     c.close();
   });
 }
 
 testSingleController() {
-  test("Single-subscription StreamController.reduce", () {
+  test("Single-subscription StreamController.fold", () {
     StreamController c = new StreamController();
     Stream stream = c.stream;
-    stream.reduce(0, (a,b) => a + b)
+    stream.fold(0, (a,b) => a + b)
     .then(expectAsync1((int v) { Expect.equals(42, v); }));
     c.add(10);
     c.add(32);
     c.close();
   });
 
-  test("Single-subscription StreamController.reduce throws", () {
+  test("Single-subscription StreamController.fold throws", () {
     StreamController c = new StreamController();
     Stream stream = c.stream;
-    stream.reduce(0, (a,b) { throw "Fnyf!"; })
+    stream.fold(0, (a,b) { throw "Fnyf!"; })
             .catchError(expectAsync1((e) { Expect.equals("Fnyf!", e.error); }));
     c.add(42);
   });
 
   test("Single-subscription StreamController.pipeInto", () {
     StreamController c = new StreamController();
     var list = <int>[];
     Stream stream = c.stream;
     stream.pipeInto(new CollectionSink<int>(list))
      .whenComplete(expectAsync0(() {
@@ skipping 365 matching lines @@
   testStream("map", (s, act) => s.map(act));
   testStream("expand", (s, act) => s.expand(act));
   testStream("where", (s, act) => s.where(act));
   testStreamError("handleError", (s, act) => s.handleError(act));
   testStreamError("handleTest", (s, act) => s.handleError((v) {}, test: act));
   testFuture("every", (s, act) => s.every(act));
   testFuture("any", (s, act) => s.any(act));
   testFuture("min", (s, act) => s.min((a, b) => act(b)));
   testFuture("max", (s, act) => s.max((a, b) => act(b)));
   testFuture("reduce", (s, act) => s.reduce(0, (a,b) => act(b)));
+  testFuture("fold", (s, act) => s.fold(0, (a,b) => act(b)));
 }
 
 main() {
   testController();
   testSingleController();
   testExtraMethods();
   testPause();
   testRethrow();
 }