Support tracing metrics for measureTime & measureFrameTime method in blink_perf

tools/perf/benchmarks/blink_perf.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function() {
 window.testRunner = {};
 window.testRunner.isDone = false;
 
 testRunner.waitUntilDone = function() {};
 testRunner.dumpAsText = function() {};
 testRunner.notifyDone = function() {
   this.isDone = true;
 };
 
+testRunner.supportTracing = true;
+
+// If this is true, blink_perf tests is put on paused waiting for tracing to
+// be started. |scheduleTestRun| should be invoked after tracing is started
+// to continue blink perf test.
+testRunner.isWaitingForTracingStart = false;
+
+testRunner.traceEventsToMeasure = undefined;
+
+testRunner.startTracing = function(tracingCategories, scheduleTestRun) {

[Xianzhu, 2017/04/21 01:31:51]

Why traceEventsToMeasure is set as a variable while tracingCategories is passed
as a parameter? Can you pass both as parameters?

[nednguyen, 2017/04/24 20:55:21]

I want to keep startTracing to be focused on setting up the trace events
required. To make the code clearer, I can refactor it to:
testRunner.startTracing(tracingCategories, scheduleTestRun) {}
testRunner.stopTracingAndMeasure(traceEventsToMeasure, callback)

wdyt?

[Xianzhu, 2017/04/24 21:03:07]

SGTM.

[nednguyen, 2017/04/24 22:31:41]

Done.

+  this.tracingCategories = tracingCategories;
+  this.scheduleTestRun = scheduleTestRun;
+  this.isWaitingForTracingStart = true;
+}
+
+testRunner.stopTracing = function() {
+}
+
 window.GCController = {};
 
 GCController.collect = function() {
   gc();
 };
 GCController.collectAll = function() {
   for (var i = 0; i < 7; ++i)
     gc();
 };
 })();