Use patching for regexp implementation.

corelib/src/implementation/regexp.dart

Index: corelib/src/implementation/regexp.dart
diff --git a/corelib/src/implementation/regexp.dart b/corelib/src/implementation/regexp.dart
new file mode 100644
index 0000000000000000000000000000000000000000..ec20e72c0f53245d2476df8af9bb12fad926f7c9
--- /dev/null
+++ b/corelib/src/implementation/regexp.dart
@@ -0,0 +1,15 @@
+// Copyright (c) 2012, 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.
+
+class JSSyntaxRegExp implements RegExp {
+  external const JSSyntaxRegExp(String pattern,
+                                [bool multiLine, bool ignoreCase]);
+  external Match firstMatch(String str);
+  external Iterable<Match> allMatches(String str);
+  external bool hasMatch(String str);
+  external String stringMatch(String str);
+  external String get pattern();
+  external bool get multiLine();
+  external bool get ignoreCase();
+}