Use metadata annotation @patch for patch classes

runtime/lib/convert_patch.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 "dart:_internal" show POWERS_OF_TEN;
 
 // JSON conversion.
 
-patch _parseJson(String json, reviver(var key, var value)) {
+@patch _parseJson(String json, reviver(var key, var value)) {
   _BuildJsonListener listener;
   if (reviver == null) {
     listener = new _BuildJsonListener();
   } else {
     listener = new _ReviverJsonListener(reviver);
   }
   var parser = new _JsonStringParser(listener);
   parser.chunk = json;
   parser.chunkEnd = json.length;
   parser.parse(0);
   parser.close();
   return listener.result;
 }
 
-patch class Utf8Decoder {
-  /* patch */
+@patch class Utf8Decoder {
+  /* @patch */
   Converter<List<int>, dynamic/*=T*/> fuse/*<T>*/(
       Converter<String, dynamic/*=T*/> next) {
     if (next is JsonDecoder) {
       return new _JsonUtf8Decoder(next._reviver, this._allowMalformed)
           as dynamic/*=Converter<List<int>, T>*/;
     }
     // TODO(lrn): Recognize a fused decoder where the next step is JsonDecoder.
     return super.fuse/*<T>*/(next);
   }
 
   // Allow intercepting of UTF-8 decoding when built-in lists are passed.
-  /* patch */
+  /* @patch */
   static String _convertIntercepted(
       bool allowMalformed, List<int> codeUnits, int start, int end) {
     return null;  // This call was not intercepted.
   }
 }
 
 class _JsonUtf8Decoder extends Converter<List<int>, Object> {
   final _Reviver _reviver;
   final bool _allowMalformed;
 
@@ skipping 1321 matching lines @@
     for (int i = 0; i < length; i++) {
       target[offset + i] = chunk.codeUnitAt(start + i);
     }
   }
 
   double parseDouble(int start, int end) {
     return _parseDouble(chunk, start, end);
   }
 }
 
-patch class JsonDecoder {
-  /* patch */ StringConversionSink startChunkedConversion(Sink<Object> sink) {
+@patch class JsonDecoder {
+  /* @patch */ StringConversionSink startChunkedConversion(Sink<Object> sink) {
     return new _JsonStringDecoderSink(this._reviver, sink);
   }
 }
 
 /**
  * Implements the chunked conversion from a JSON string to its corresponding
  * object.
  *
  * The sink only creates one object, but its input can be chunked.
  */
@@ skipping 376 matching lines @@
     _parser.parse(start);
   }
 
   void close() {
     _parser.close();
     var decoded = _parser.result;
     _sink.add(decoded);
     _sink.close();
   }
 }