Fix dart2js compilation error in previous commit

tests/standalone/io/http_stream_close_test.dart

Index: tests/standalone/io/http_stream_close_test.dart
diff --git a/tests/standalone/io/http_stream_close_test.dart b/tests/standalone/io/http_stream_close_test.dart
index 1f6d65b21161cc2bac53bf44cb179109c4834d4f..4ccb6685bd4f8113cbe82d672f6b0efeab2d88f6 100644
--- a/tests/standalone/io/http_stream_close_test.dart
+++ b/tests/standalone/io/http_stream_close_test.dart
@@ -34,11 +34,12 @@ main() {
     };
   };
 
-  var connection = client.postUrl(new Uri.fromString("http://127.0.0.1:${server.port}"));
-  connection.onError = (e) => throw e;
+  var connection = client.postUrl(
+      new Uri.fromString("http://127.0.0.1:${server.port}"));
+  connection.onError = (e) { throw e; };
   connection.onRequest = (request) {
     request.contentLength = "hello!".length;
-    request.outputStream.onError = (e) => throw e;
+    request.outputStream.onError = (e) { throw e; };
     request.outputStream.onClosed = () {
       clientOnClosed = true;
       checkDone();