[WIP] Port media metrics to TBMv2

telemetry/telemetry/internal/actions/seek.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 seekMedia(selector, seekTime, logSeekTime, seekLabel) {
     // Performs the "Seek" action on media satisfying selector.
     var mediaElements = window.__findMediaElements(selector);
     for (var i = 0; i < mediaElements.length; i++) {
@@ skipping 27 matching lines @@
     window.__registerHTML5EventCompleted(element, 'seeked');
 
     if (logSeekTime) {
       var willSeekEvent = document.createEvent('Event');
       willSeekEvent.initEvent('willSeek', false, false);
       if (seekLabel)
         willSeekEvent.seekLabel = seekLabel;
       else
         willSeekEvent.seekLabel = seekTime;
       element.dispatchEvent(willSeekEvent);
+      performance.mark('seekLabel-' + willSeekEvent.seekLabel);
     }
     try {
       element.currentTime = seekTime;
     } catch (err) {
       throw new Error('Cannot seek in network state: ' + element.networkState);
     }
   }
 
   window.__seekMedia = seekMedia;
 })();