Make StreamController be a StreamSink, not just an EventSink.

tests/lib/async/stream_controller_test.dart

Index: tests/lib/async/stream_controller_test.dart
diff --git a/tests/lib/async/stream_controller_test.dart b/tests/lib/async/stream_controller_test.dart
index b4aa6aa47ffbe5e6ebf9a54d67954a14b6eff8ef..439121c10f67f69219b9b0045e941e96ce0175da 100644
--- a/tests/lib/async/stream_controller_test.dart
+++ b/tests/lib/async/stream_controller_test.dart
@@ -9,7 +9,7 @@ import "package:expect/expect.dart";
 import 'dart:async';
 import 'event_helper.dart';
 
-testMultiController() {
+void testMultiController() {
   // Test normal flow.
   var c = new StreamController(sync: true);
   Events expectedEvents = new Events()
@@ -408,7 +408,7 @@ testExtraMethods() {
   Expect.listEquals(expectedEvents.events, actualEvents.events);
 }
 
-testClosed() {
+void testClosed() {
   StreamController c = new StreamController(sync: true);
   Expect.isFalse(c.isClosed);
   c.add(42);