Revert "Ensure that failure to start an isolate all end up in the future."

tests/isolate/isolate_create_error_helper_lib4.dart

Index: tests/isolate/isolate_create_error_helper_lib4.dart
diff --git a/tests/isolate/isolate_create_error_helper_lib4.dart b/tests/isolate/isolate_create_error_helper_lib4.dart
deleted file mode 100644
index 294e854563f240be1870fc25e8e44e5a8cb000d0..0000000000000000000000000000000000000000
--- a/tests/isolate/isolate_create_error_helper_lib4.dart
+++ /dev/null
@@ -1,10 +0,0 @@
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library isolate.create.error_helper4_lib;
-
-// This library has a main that is not a function,
-// but does have a function type.
-
-final main = () { print("Not a function declaration!"); };