[Telemetry] Improve logging on media measurement tests.

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 45 matching lines @@
       }, 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)
+    if (this.element.id)
+      this.id = this.element.id;
+    else 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;
     else
       this.id = 'media_' + window.__globalCounter++;
   };
 
   HTMLMediaMetric.prototype.onWillPlay = function(e) {
     this.playbackTimer = new Timer();
   };
 
   HTMLMediaMetric.prototype.onWillSeek = function(e) {
     var seekLabel = '';
@@ skipping 108 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;
 })();