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

tests/isolate/global_error_handler_stream_test.dart

Index: tests/isolate/global_error_handler_stream_test.dart
diff --git a/tests/isolate/global_error_handler_stream_test.dart b/tests/isolate/global_error_handler_stream_test.dart
index 5c094872b0f6936228625f5de89dd505dba68696..4fcd8bf043a94a5a72e76009a3900c3f35e2e85b 100644
--- a/tests/isolate/global_error_handler_stream_test.dart
+++ b/tests/isolate/global_error_handler_stream_test.dart
@@ -19,7 +19,7 @@ void runFunctions() {
   }
 }
 
-void startTest(StreamSink finishSink) {
+void startTest(EventSink finishSink) {
   firstFunction = () { throw new RuntimeError("ignore exception"); };
   finishFunction = () { finishSink.add("done"); finishSink.close(); };
   new Timer(Duration.ZERO, runFunctions);
@@ -36,7 +36,7 @@ bool globalErrorHandler(IsolateUnhandledException e) {
 main() {
   var box = new MessageBox();
   var timer;
-  StreamSink otherIsolate = streamSpawnFunction(runTest, globalErrorHandler);
+  EventSink otherIsolate = streamSpawnFunction(runTest, globalErrorHandler);
   otherIsolate.add(box.sink);
   otherIsolate.close();
   box.stream.single.then((msg) {