Add Telemetry media loop action.

tools/perf/metrics/media.js

 // Copyright 2013 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.
 
 // This file contains common utilities to find video/audio elements on a page
 // and collect metrics for each.
 
 (function() {
   // MediaMetric class responsible for collecting metrics on a media element.
   // It attaches required event listeners in order to collect different metrics.
@@ skipping 36 matching lines @@
       });
     this.setID();
 
     // Listen to when a Telemetry actions gets called.
     this.element.addEventListener('willPlay', function (e) {
         metric.onWillPlay(e);
       }, false);
     this.element.addEventListener('willSeek', function (e) {
         metric.onWillSeek(e);
       }, false);
+    this.element.addEventListener('willLoop', function (e) {
+        metric.onWillLoop(e);
+      }, false);
   }
 
   HTMLMediaMetric.prototype = new MediaMetricBase();
   HTMLMediaMetric.prototype.constructor = HTMLMediaMetric;
 
   HTMLMediaMetric.prototype.setID = function() {
     if (this.element.src)
       this.id = this.element.src.substring(this.element.src.lastIndexOf("/")+1);
     else if (this.element.id)
       this.id = this.element.id;
@@ skipping 11 matching lines @@
       seekLabel = '_' + e.seekLabel;
     var metric = this;
     var onSeeked = function(e) {
         metric.appendMetric('seek' + seekLabel, metric.seekTimer.stop())
         e.target.removeEventListener('seeked', onSeeked);
       };
     this.seekTimer = new Timer();
     this.element.addEventListener('seeked', onSeeked);
   };
 
+  HTMLMediaMetric.prototype.onWillLoop = function(e) {
+    var loopTimer = new Timer();
+    var metric = this;
+    var loopCount = e.loopCount;
+    var onEndLoop = function(e) {
+        var actualDuration = loopTimer.stop();
+        var idealDuration = metric.element.duration * loopCount;
+        var avg_loop_time = (actualDuration - idealDuration) / loopCount;
+        metric.metrics['avg_loop_time'] = avg_loop_time.toFixed(3);
+        e.target.removeEventListener('endLoop', onEndLoop);
+      };
+    this.element.addEventListener('endLoop', onEndLoop);
+  };
+
   HTMLMediaMetric.prototype.appendMetric = function(metric, value) {
     if (!this.metrics[metric])
       this.metrics[metric] = [];
     this.metrics[metric].push(value);
   }
 
   HTMLMediaMetric.prototype.onPlaying = function(event) {
     // Playing event can fire more than once if seeking.
     if (!this.metrics['time_to_play'])
       this.metrics['time_to_play'] = this.playbackTimer.stop();
@@ skipping 69 matching lines @@
     for (var i = 0; i < window.__mediaMetrics.length; i++)
       metrics.push(window.__mediaMetrics[i].getSummary());
     return metrics;
   }
 
   window.__globalCounter = 0;
   window.__mediaMetrics = [];
   window.__getAllMetrics = getAllMetrics;
   window.__createMediaMetricsForDocument = createMediaMetricsForDocument;
 })();