isolates refactor: this change introduces 'dart:isolate' as a library. This is a

tests/isolate/src/IsolateImportNegativeTest.dart

Index: tests/isolate/src/IsolateImportNegativeTest.dart
diff --git a/tests/standalone/src/TimeoutTest.dart b/tests/isolate/src/IsolateImportNegativeTest.dart
similarity index 52%
copy from tests/standalone/src/TimeoutTest.dart
copy to tests/isolate/src/IsolateImportNegativeTest.dart
index 15e9647652002a2d156b91340758b7c06a244e3d..80e43421cfc6621efc35c9eaea6e5ff7edfabd24 100644
--- a/tests/standalone/src/TimeoutTest.dart
+++ b/tests/isolate/src/IsolateImportNegativeTest.dart
@@ -2,9 +2,17 @@
 // 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('IsolateImportNegativeTest');
+// Ommiting the following import is an error:
+// #import('dart:isolate');
 
-// A test that runs forever.
-void main() {
-  new ReceivePort().receive((x, y) => null);
-  // Does not close the receive port.
+class A extends Isolate {
+  A() : super();
+
+  void main() {}
+}
+
+main() {
+  new A();
 }
+