Update timer and adjust frequency.

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 2bdc2c531b01b6d4a8305400e393aaea3b8f2d19..e16005cab8652c6477803310a6e76e47eca74406 100644
--- a/runtime/lib/stopwatch_patch.dart
+++ b/runtime/lib/stopwatch_patch.dart
@@ -5,9 +5,15 @@
 // A VM patch of the stopwatch part of dart:core.
 
 patch class Stopwatch {
+  /* patch */ static void _initTicker() {
+    if (_frequency == null) {
+      _frequency = _computeFrequency();
+    }
+  }
+
   // Returns the current clock tick.
   /* patch */ static int _now() native "Stopwatch_now";
 
   // Returns the frequency of clock ticks in Hz.
-  /* patch */ static int _frequency() native "Stopwatch_frequency";
+  static int _computeFrequency() native "Stopwatch_frequency";
 }