Use metadata annotation @patch for patch classes

runtime/lib/string_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.
 
 const int _maxAscii = 0x7f;
 const int _maxLatin1 = 0xff;
 const int _maxUtf16 = 0xffff;
 const int _maxUnicode = 0x10ffff;
 
-patch class String {
-  /* patch */ factory String.fromCharCodes(Iterable<int> charCodes,
-                                           [int start = 0, int end]) {
+@patch class String {
+  /* @patch */ factory String.fromCharCodes(Iterable<int> charCodes,
+                                            [int start = 0, int end]) {
     if (charCodes is! Iterable) throw new ArgumentError.value(charCodes, "charCodes");
     if (start is! int) throw new ArgumentError.value(start, "start");
     if (end != null && end is! int) throw new ArgumentError.value(end, "end");
     return _StringBase.createFromCharCodes(charCodes, start, end, null);
   }
 
-  /* patch */ factory String.fromCharCode(int charCode) {
+  /* @patch */ factory String.fromCharCode(int charCode) {
     if (charCode >= 0) {
       if (charCode <= 0xff) {
         return _OneByteString._allocate(1).._setAt(0, charCode);
       }
       if (charCode <= 0xffff) {
         return _StringBase._createFromCodePoints(new _List(1)..[0] = charCode,
                                                  0, 1);
       }
       if (charCode <= 0x10ffff) {
         var low = 0xDC00 | (charCode & 0x3ff);
         int bits = charCode - 0x10000;
         var high = 0xD800 | (bits >> 10);
         return  _StringBase._createFromCodePoints(new _List(2)..[0] = high
                                                               ..[1] = low,
                                                   0, 2);
       }
     }
     throw new RangeError.range(charCode, 0, 0x10ffff);
   }
 
-  /* patch */ const factory String.fromEnvironment(String name,
-                                                   {String defaultValue})
+  /* @patch */ const factory String.fromEnvironment(String name,
+                                                    {String defaultValue})
       native "String_fromEnvironment";
 }
 
 
 /**
  * [_StringBase] contains common methods used by concrete String
  * implementations, e.g., _OneByteString.
  */
 abstract class _StringBase {
   // Constants used by replaceAll encoding of string slices between matches.
@@ skipping 1307 matching lines @@
     int end = index + _pattern.length;
     _current = new _StringMatch(index, _input, _pattern);
     // Empty match, don't start at same location again.
     if (end == _index) end++;
     _index = end;
     return true;
   }
 
   Match get current => _current;
 }