[WIP] Port media metrics to TBMv2

telemetry/telemetry/internal/actions/play.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 performs actions on media elements.
 (function() {
   function playMedia(selector) {
     // Performs the "Play" action on media satisfying selector.
     var mediaElements = window.__findMediaElements(selector);
     for (var i = 0; i < mediaElements.length; i++) {
       console.log('Playing element: ' + mediaElements[i].src);
       play(mediaElements[i]);
     }
   }
 
   function play(element) {
     if (element instanceof HTMLMediaElement)
       playHTML5Element(element);
     else
       throw new Error('Can not play non HTML5 media elements.');
   }
 
   function playHTML5Element(element) {
     window.__registerHTML5ErrorEvents(element);
     window.__registerHTML5EventCompleted(element, 'playing');
     window.__registerHTML5EventCompleted(element, 'ended');
+    element.addEventListener('durationchange', function(e) {
+      performance.mark('duration-' + element.duration);
+    });
 
     var willPlayEvent = document.createEvent('Event');
     willPlayEvent.initEvent('willPlay', false, false);
     element.dispatchEvent(willPlayEvent);
     element.play();
   }
 
   window.__playMedia = playMedia;
 })();