Make StreamController's unnamed constructor create a single-sub stream.

tests/lib/async/stream_single_to_multi_subscriber_test.dart

Index: tests/lib/async/stream_single_to_multi_subscriber_test.dart
diff --git a/tests/lib/async/stream_single_to_multi_subscriber_test.dart b/tests/lib/async/stream_single_to_multi_subscriber_test.dart
index 0ef7a26f5479dd30cd0078c02e21bd55763180b8..3feb0497f2e0221d7e9d29f64faa0900682b5315 100644
--- a/tests/lib/async/stream_single_to_multi_subscriber_test.dart
+++ b/tests/lib/async/stream_single_to_multi_subscriber_test.dart
@@ -12,7 +12,7 @@ import 'event_helper.dart';
 
 main() {
   test("tomulti 1", () {
-    StreamController c = new StreamController<int>.singleSubscription();
+    StreamController c = new StreamController<int>();
     Stream<int> multi = c.stream.asMultiSubscriberStream();
     // Listen twice.
     multi.listen(expectAsync1((v) => Expect.equals(42, v)));
@@ -21,7 +21,7 @@ main() {
   });
 
   test("tomulti 2", () {
-    StreamController c = new StreamController<int>.singleSubscription();
+    StreamController c = new StreamController<int>();
     Stream<int> multi = c.stream.asMultiSubscriberStream();
     Events expected = new Events.fromIterable([1, 2, 3, 4, 5]);
     Events actual1 = new Events.capture(multi);
@@ -36,7 +36,7 @@ main() {
   });
 
   test("tomulti no-op", () {
-    StreamController c = new StreamController<int>();
+    StreamController c = new StreamController<int>.multiSubscription();
     Stream<int> multi = c.stream.asMultiSubscriberStream();
     Events expected = new Events.fromIterable([1, 2, 3, 4, 5]);
     Events actual1 = new Events.capture(multi);