Port and integrate the irregexp engine from V8

tests/language/regex/malformed-escapes_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 handling of malformed escape sequences."
+  );
+
+  var regexp;
+
+  regexp = new RegExp(r"\ug", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('ug'));
+
+  regexp = new RegExp(r"\xg", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('xg'));
+
+  regexp = new RegExp(r"\c_", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('\\\\c_'));
+
+  regexp = new RegExp(r"[\B]", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('B'));
+
+  regexp = new RegExp(r"[\b]", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('\b'));
+
+  regexp = new RegExp(r"\8", multiLine: true);
+  shouldBeTrue(regexp.hasMatch('\\\8'));
+
+  regexp = new RegExp(r"^[\c]$");
+  shouldBeTrue(regexp.hasMatch('c'));
+
+  regexp = new RegExp(r"^[\c_]$");
+  shouldBeFalse(regexp.hasMatch('c'));
+
+  regexp = new RegExp(r"^[\c]]$");
+  shouldBeTrue(regexp.hasMatch('c]'));
+}