Don't use Uint32List in IO test

tests/standalone/io/http_head_test.dart

Index: tests/standalone/io/http_head_test.dart
diff --git a/tests/standalone/io/http_head_test.dart b/tests/standalone/io/http_head_test.dart
index 56cc54fb51fcd3b448ceda532113b898b1eb8b8c..84e03e85c9468e2e9ddea3d80dd0f1de990d16f2 100644
--- a/tests/standalone/io/http_head_test.dart
+++ b/tests/standalone/io/http_head_test.dart
@@ -18,7 +18,7 @@ void testHEAD(int totalConnections) {
       (request) => request.path == "/test200",
       (HttpRequest request, HttpResponse response) {
         response.contentLength = 200;
-        List<int> data = new Uint32List(200);
+        List<int> data = new List<int>(200);
         response.outputStream.write(data);
         response.outputStream.close();
       });