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

third_party/WebKit/LayoutTests/media/video-controls-hidden-audio.html

 <video controls></video>
 <p>Test that hiding volume / mute buttons works as expected.</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 src=media-controls.js></script>
 <script>
     video.src = findMediaFile("video", "content/test");
     run("video.load()");
     waitForEvent("canplaythrough", function () {
         // Enable hidden audio preferences to take effect.
         run("window.internals.setAllowHiddenVolumeControls(video, true)");
         // Request non-hidden audio controls.
         run("window.internals.settings.setPreferHiddenVolumeControls(false)");
@@ skipping 21 matching lines @@
         // For muted video, the volume slider will hide but the mute
         // button should stay, since we always have it present for media
         // which have audio.
         run("video.muted = true");
         testExpected("getComputedStyle(muteButton).display", "none", '!=');
         testExpected("getComputedStyle(volumeSlider).display", "none", '==');
 
         endTest();
     });
 </script>