Implement @patch annotation for patch class members

runtime/lib/stopwatch_patch.dart

Index: runtime/lib/stopwatch_patch.dart
diff --git a/runtime/lib/stopwatch_patch.dart b/runtime/lib/stopwatch_patch.dart
index e3749e848c0742effabbe11c2c7f99a167fc4b7d..2560243aab0cdc02e8243b62d94c95f7dcc00089 100644
--- a/runtime/lib/stopwatch_patch.dart
+++ b/runtime/lib/stopwatch_patch.dart
@@ -5,14 +5,14 @@
 // A VM patch of the stopwatch part of dart:core.
 
 @patch class Stopwatch {
-  /* @patch */ static void _initTicker() {
+  @patch static void _initTicker() {
     if (_frequency == null) {
       _frequency = _computeFrequency();
     }
   }
 
   // Returns the current clock tick.
-  /* @patch */ static int _now() native "Stopwatch_now";
+  @patch static int _now() native "Stopwatch_now";
 
   // Returns the frequency of clock ticks in Hz.
   static int _computeFrequency() native "Stopwatch_frequency";