Refactor prepareToMeasureValuesAsync to startMeasureValuesAsyn which run test through callback

third_party/WebKit/PerformanceTests/Bindings/post-message.html

Index: third_party/WebKit/PerformanceTests/Bindings/post-message.html
diff --git a/third_party/WebKit/PerformanceTests/Bindings/post-message.html b/third_party/WebKit/PerformanceTests/Bindings/post-message.html
index 5745861725132670f3077a95aa054a06e76a1375..3655a1000247d0896f4edc4342a383f2a42cb079 100644
--- a/third_party/WebKit/PerformanceTests/Bindings/post-message.html
+++ b/third_party/WebKit/PerformanceTests/Bindings/post-message.html
@@ -30,9 +30,11 @@ window.onload = function () {
     PerfTestRunner.prepareToMeasureValuesAsync({
         description: "Measures time to run 1000 postMessage round trips in serial.",
         unit: 'ms',
+        run: function() {
+            runTest();
+        },

[Xianzhu, 2017/05/03 22:06:25]

Nit: a simpler way is
  run: runTest,

[nednguyen, 2017/05/04 00:10:32]

Done.

         done: testDone,
     });
-    runTest();
 };
 </script>
 <div id="log"></div>