Remove StreamSink(replaced by EventSink) and make IOSink extend EventSink.

sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
index f47100ec7a8ddfaeb48369ed0fcf5ea516f19d0a..743dbf9a307954d6646432e4954bc90d1d4bcd1d 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/isolate_helper.dart
@@ -24,7 +24,7 @@ class CloseToken {
   const CloseToken();
 }
 
-class JsIsolateSink extends StreamSink<dynamic> implements IsolateSink {
+class JsIsolateSink extends EventSink<dynamic> implements IsolateSink {
   bool _isClosed = false;
   final SendPort _port;
   JsIsolateSink.fromPort(this._port);