Retain script path of parent isolate when spawnFunction is called so that

tests/standalone/issue14236_source.dart

+// Copyright (c) 2013, 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.
+//
+// This is the original dart program that was used to generate the snapshot
+// in file issue14236_test.dart
+// The original main has been commented out and we have a main which
+// throws an error to ensure that this file is not executed as part of the
+// test.
+
+library test.issue14236;
+import 'dart:isolate';
+import "package:expect/expect.dart";
+
+test() {
+  port.receive((msg, reply) => reply.send(msg));
+}
+
+/*
+main() {
+  ReceivePort port = new ReceivePort();
+  port.receive((msg, reply) => port.close());
+
+  SendPort s = spawnFunction(test);
+  s.send('hi', port.toSendPort());
+}
+*/
+
+main() {
+  Expect.fail("Don't expect this to run at all");
+}