HTTP loading tests and package root support

tests/standalone/http_launch_data/http_isolate_main.dart

Index: tests/standalone/http_launch_data/http_isolate_main.dart
diff --git a/tests/language/issue9664_test.dart b/tests/standalone/http_launch_data/http_isolate_main.dart
similarity index 71%
copy from tests/language/issue9664_test.dart
copy to tests/standalone/http_launch_data/http_isolate_main.dart
index b8b3c2db6b6277c62393bd7e44f03b26292eaf37..ba7a59de5838ac18109f96e89d183fa53fab5a3a 100644
--- a/tests/language/issue9664_test.dart
+++ b/tests/standalone/http_launch_data/http_isolate_main.dart
@@ -2,8 +2,10 @@
 // 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.
 
-// Regression test for http://dartbug.com/9664
+import 'dart:isolate';
 
 main() {
-  while (true ? true : true) break;
+  port.receive((message, replyTo) {
+    replyTo.call(message);
+  });
 }