[Telemetry] Improve logging on media measurement tests.

tools/telemetry/telemetry/page/actions/seek.js

Index: tools/telemetry/telemetry/page/actions/seek.js
diff --git a/tools/telemetry/telemetry/page/actions/seek.js b/tools/telemetry/telemetry/page/actions/seek.js
index 1a06ed10e985de239fde57b8d67d5e113c5b9f8e..e77d48726db139aacbbdf1eb84fdcd38c4e06ad5 100644
--- a/tools/telemetry/telemetry/page/actions/seek.js
+++ b/tools/telemetry/telemetry/page/actions/seek.js
@@ -4,35 +4,34 @@
 
 // This file performs actions on media elements.
 (function() {
-  function seekMedia(selector, seekTime, logSeekTime) {
+  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++) {
-      seek(mediaElements[i], seekTime, logSeekTime);
+      if (mediaElements[i] instanceof HTMLMediaElement)
+        seekHTML5Element(mediaElements[i], seekTime, logSeekTime, seekLabel);
+      else
+        throw new Error('Can not seek non HTML5 media elements.');
     }
   }
 
-  function seek(element, seekTime, logSeekTime) {
-    if (element instanceof HTMLMediaElement)
-      seekHTML5Element(element, seekTime, logSeekTime);
-    else
-      throw new Error('Can not seek non HTML5 media elements.');
-  }
-
-  function seekHTML5Element(element, seekTime, logSeekTime) {
+  function seekHTML5Element(element, seekTime, logSeekTime, seekLabel) {
+    function readyForSeek() {
+      seekHTML5ElementPostLoad(element, seekTime, logSeekTime, seekLabel);
+    }
     if (element.readyState == element.HAVE_NOTHING) {
       var onLoadedMetaData = function(e) {
         element.removeEventListener('loadedmetadata', onLoadedMetaData);
-        seekHTML5ElementPostLoad(element, seekTime, logSeekTime);
+        readyForSeek();
       };
       element.addEventListener('loadedmetadata', onLoadedMetaData);
       element.load();
     } else {
-      seekHTML5ElementPostLoad(element, seekTime, logSeekTime);
+      readyForSeek();
     }
   }
 
-  function seekHTML5ElementPostLoad(element, seekTime, logSeekTime) {
+  function seekHTML5ElementPostLoad(element, seekTime, logSeekTime, seekLabel) {
     var onSeeked = function(e) {
       element[e.type + '_completed'] = true;
       element.removeEventListener('seeked', onSeeked);
@@ -49,7 +48,10 @@
     if (logSeekTime) {
       var willSeekEvent = document.createEvent('Event');
       willSeekEvent.initEvent('willSeek', false, false);
-      willSeekEvent.seekLabel = seekTime;
+      if (seekLabel)
+        willSeekEvent.seekLabel = seekLabel;
+      else
+        willSeekEvent.seekLabel = seekTime;
       element.dispatchEvent(willSeekEvent);
     }
     try {