Use metadata annotation @patch for patch classes

runtime/lib/array_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.
 
 // The _GrowableArrayMarker class is used to signal to the List() factory
 // whether a parameter was passed.
 class _GrowableArrayMarker implements int {
   const _GrowableArrayMarker();
 }
 
 const _GROWABLE_ARRAY_MARKER = const _GrowableArrayMarker();
 
-patch class List<E> {
-  /* patch */ factory List([int length = _GROWABLE_ARRAY_MARKER]) {
+@patch class List<E> {
+  /* @patch */ factory List([int length = _GROWABLE_ARRAY_MARKER]) {
     if (identical(length, _GROWABLE_ARRAY_MARKER)) {
       return new _GrowableList<E>(0);
     }
     // All error handling on the length parameter is done at the implementation
     // of new _List.
     return new _List<E>(length);
   }
 
-  /* patch */ factory List.filled(int length, E fill, {bool growable: false}) {
+  /* @patch */ factory List.filled(int length, E fill, {bool growable: false}) {
     // All error handling on the length parameter is done at the implementation
     // of new _List.
     var result = growable ? new _GrowableList<E>(length) : new _List<E>(length);
     if (fill != null) {
       for (int i = 0; i < length; i++) {
         result[i] = fill;
       }
     }
     return result;
   }
 
-  /* patch */ factory List.from(Iterable elements, { bool growable: true }) {
+  /* @patch */ factory List.from(Iterable elements, { bool growable: true }) {
     if (elements is EfficientLength) {
       int length = elements.length;
       var list = growable ? new _GrowableList<E>(length) : new _List<E>(length);
       if (length > 0) {  // Avoid creating iterator unless necessary.
         int i = 0;
         for (var element in elements) { list[i++] = element; }
       }
       return list;
     }
     List<E> list = new _GrowableList<E>(0);
     for (E e in elements) {
       list.add(e);
     }
     if (growable) return list;
     if (list.length == 0) {
       // Avoid getting an immutable list from makeListFixedLength.
       return new _List<E>(0);
     }
     return makeListFixedLength(list);
   }
 
-  /* patch */ factory List.unmodifiable(Iterable elements) {
+  /* @patch */ factory List.unmodifiable(Iterable elements) {
     List result = new List<E>.from(elements, growable: false);
     return makeFixedListUnmodifiable(result);
   }
 
   // Factory constructing a mutable List from a parser generated List literal.
   // [elements] contains elements that are already type checked.
   factory List._fromLiteral(List elements) {
     if (elements.isEmpty) {
       return new _GrowableList<E>(0);
     }
     var result = new _GrowableList<E>.withData(elements);
     result._setLength(elements.length);
     return result;
   }
 }