Port regexp tests from V8 to Dart.

tests/corelib/regexp/quantified-assertions_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(
+  "This page tests assertions followed by quantifiers."
+  );
+
+  var regexp;
+
+  regexp = new RegExp(r"(?=a){0}", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('a'));
+
+  regexp = new RegExp(r"(?=a){1}", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('a'));
+
+  regexp = new RegExp(r"(?!a){0}", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('b'));
+
+  regexp = new RegExp(r"(?!a){1}", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('b'));
+
+  shouldBeTrue(new RegExp(r"^(?=a)?b$").hasMatch("b"));
+}