Port regexp tests from V8 to Dart.

tests/corelib/regexp/non-capturing-backtracking_test.dart

Index: tests/corelib/regexp/non-capturing-backtracking_test.dart
diff --git a/tests/language/deferred_only_constant_test.dart b/tests/corelib/regexp/non-capturing-backtracking_test.dart
similarity index 55%
copy from tests/language/deferred_only_constant_test.dart
copy to tests/corelib/regexp/non-capturing-backtracking_test.dart
index e50d7ba6a1537a687787b7659fb528b57ce85746..3bf3c7702d0181e91a69488ca8a337648c789ebd 100644
--- a/tests/language/deferred_only_constant_test.dart
+++ b/tests/corelib/regexp/non-capturing-backtracking_test.dart
@@ -2,14 +2,14 @@
 // 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.
 
-// Testing import of only constants from a deferred library.
-
+import 'util.dart';
 import 'package:expect/expect.dart';
 
-import "deferred_only_constant_lib.dart" deferred as lib;
-
 void main() {
-  lib.loadLibrary().then((_) {
-    Expect.equals(lib.constant, const ["a", "b", "c"]);
-  });
-}
+  description(
+  "This page tests for proper backtracking with greedy quantifiers and non-capturing parentheses."
+  );
+
+  var re = new RegExp(r"(?:a*)a");
+  shouldBe(re.firstMatch('a'), ['a']);
+}