Make new StreamController be async by default.

tests/standalone/io/zlib_test.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.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
 void testZLibDeflate() {
   test(int level, List<int> expected) {
     var port = new ReceivePort();
     var data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
-    var controller = new StreamController();
+    var controller = new StreamController(sync: true);
     controller.stream.transform(new ZLibDeflater(gzip: false, level: level))
         .fold([], (buffer, data) {
           buffer.addAll(data);
           return buffer;
         })
         .then((data) {
           Expect.listEquals(expected, data);
           port.close();
         });
     controller.add(data);
     controller.close();
   }
   test(6, [120, 156, 99, 96, 100, 98, 102, 97, 101, 99, 231, 224, 4, 0, 0, 175,
            0, 46]);
 }
 
 
 void testZLibDeflateEmpty() {
   var port = new ReceivePort();
-  var controller = new StreamController();
+  var controller = new StreamController(sync: true);
   controller.stream.transform(new ZLibDeflater(gzip: false, level: 6))
       .fold([], (buffer, data) {
         buffer.addAll(data);
         return buffer;
       })
       .then((data) {
         Expect.listEquals([120, 156, 3, 0, 0, 0, 0, 1], data);
         port.close();
       });
   controller.close();
 }
 
 
 void testZLibDeflateGZip() {
   var port = new ReceivePort();
   var data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
-  var controller = new StreamController();
+  var controller = new StreamController(sync: true);
   controller.stream.transform(new ZLibDeflater())
       .fold([], (buffer, data) {
         buffer.addAll(data);
         return buffer;
       })
       .then((data) {
         Expect.equals(30, data.length);
         Expect.listEquals([99, 96, 100, 98, 102, 97, 101, 99, 231, 224, 4, 0,
                            70, 215, 108, 69, 10, 0, 0, 0],
                           // Skip header, as it can change.
@@ skipping 23 matching lines @@
   test(10);
   test(42);
   test(null);
   test("9");
 }
 
 void testZLibInflate() {
   test2(bool gzip, int level) {
     var port = new ReceivePort();
     var data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
-    var controller = new StreamController();
+    var controller = new StreamController(sync: true);
     controller.stream
       .transform(new ZLibDeflater(gzip: gzip, level: level))
       .transform(new ZLibInflater())
         .fold([], (buffer, data) {
           buffer.addAll(data);
           return buffer;
         })
         .then((inflated) {
           Expect.listEquals(data, inflated);
           port.close();
@@ skipping 10 matching lines @@
   }
 }
 
 void main() {
   testZLibDeflate();
   testZLibDeflateEmpty();
   testZLibDeflateGZip();
   testZLibDeflateInvalidLevel();
   testZLibInflate();
 }