Use metadata annotation @patch for patch classes

runtime/lib/double_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.
 // Dart core library.
 
 // VM implementation of double.
 
-patch class double {
+@patch class double {
 
   static double _nativeParse(String str,
                              int start, int end) native "Double_parse";
 
   static double _tryParseDouble(var str, var start, var end) {
     assert(start < end);
     const int _DOT = 0x2e;    // '.'
     const int _ZERO = 0x30;   // '0'
     const int _MINUS = 0x2d;  // '-'
     const int _N = 0x4e;      // 'N'
@@ skipping 75 matching lines @@
     int len = str.length;
     int start = str._firstNonWhitespace();
     if (start == len) return null;  // All whitespace.
     int end = str._lastNonWhitespace() + 1;
     assert(start < end);
     var result = _tryParseDouble(str, start, end);
     if (result != null) return result;
     return _nativeParse(str, start, end);
   }
 
-  /* patch */ static double parse(String str,
-                                  [double onError(String str)]) {
+  /* @patch */ static double parse(String str,
+                                   [double onError(String str)]) {
     var result = _parse(str);
     if (result == null) {
       if (onError == null) throw new FormatException("Invalid double", str);
       return onError(str);
     }
     return result;
   }
 }