Port regexp tests from V8 to Dart.

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

+// 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.
+
+import 'util.dart';
+import 'package:expect/expect.dart';
+
+void main() {
+  description(
+  'Test for behavior of non-capturing groups, as described in <a href="http://blog.stevenlevithan.com/archives/npcg-javascript">' +
+  'a blog post by Steven Levithan</a> and <a href="http://bugs.webkit.org/show_bug.cgi?id=14931">bug 14931</a>.'
+  );
+
+  shouldBeTrue(new RegExp(r"(x)?\1y").hasMatch("y"));
+  shouldBe(new RegExp(r"(x)?\1y").firstMatch("y"), ["y", null]);
+  shouldBe(new RegExp(r"(x)?y").firstMatch("y"), ["y", null]);
+  shouldBe(firstMatch("y", new RegExp(r"(x)?\1y")), ["y", null]);
+  shouldBe(firstMatch("y", new RegExp(r"(x)?y")), ["y", null]);
+  shouldBe(firstMatch("y", new RegExp(r"(x)?\1y")), ["y", null]);
+  Expect.listEquals("y".split(new RegExp(r"(x)?\1y")), ["", ""]);
+  Expect.listEquals("y".split(new RegExp(r"(x)?y")), ["", ""]);
+  assertEquals("y".indexOf(new RegExp(r"(x)?\1y")), 0);
+  assertEquals("y".replaceAll(new RegExp(r"(x)?\1y"), "z"), "z");
+  assertEquals("y".replaceAllMapped(new RegExp(r"(x)?y"), (m) => m.group(1)), "null");
+  assertEquals("y".replaceAllMapped(new RegExp(r"(x)?\1y"), (m) => m.group(1)), "null");
+  assertEquals("y".replaceAllMapped(new RegExp(r"(x)?y"), (m) => m.group(1)), "null");
+}