Use metadata annotation @patch for patch classes

runtime/lib/regexp_patch.dart

 // 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.
 
 import "dart:collection" show LinkedList, LinkedListEntry;
 
-patch class RegExp {
-  /* patch */ factory RegExp(String source,
-                             {bool multiLine: false,
-                              bool caseSensitive: true}) {
+@patch class RegExp {
+  /* @patch */ factory RegExp(String source,
+                              {bool multiLine: false,
+                               bool caseSensitive: true}) {
     _RegExpHashKey key = new _RegExpHashKey(
         source, multiLine, caseSensitive);
     _RegExpHashValue value = _cache[key];
 
     if (value == null) {
       if (_cache.length > _MAX_CACHE_SIZE) {
         _RegExpHashKey lastKey = _recentlyUsed.last;
         lastKey.unlink();
         _cache.remove(lastKey);
       }
@@ skipping 253 matching lines @@
           _nextIndex++;
         }
         return true;
       }
     }
     _current = null;
     _re = null;
     return false;
   }
 }