Add TODOs to convert from video-test.js to testharness.js

third_party/WebKit/LayoutTests/media/video-seeking.html

 <video controls></video>
 <p>Test that seeking attribute is true immediately after a seek,
  goes back to false when seeking completes, and that a 'seeked' event
  is fired for each seek
  </p>
 <script src=media-file.js></script>
+<!-- TODO(philipj): Convert test to testharness.js. crbug.com/588956
+     (Please avoid writing new tests using video-test.js) -->
 <script src=video-test.js></script>
 <script>
 
     var seekedCount = 0;
 
     function seeked()
     {
         ++seekedCount;
         consoleWrite("");
 
@@ skipping 20 matching lines @@
         run("video.currentTime = 0.5");
         consoleWrite("");
     }
 
     waitForEvent('waiting' );
     waitForEvent('seeked', seeked );
     waitForEventOnce('canplaythrough', canplaythrough);
 
     video.src = findMediaFile("video", "content/test");
 </script>