Convert video-controls-[captions, overlay, track]* tests to testharness.js

Cleaning up video-controls-[captions, overlay, track]* tests
in media/ to use testharness.js instead of video-test.js.
This will enable to upstream these tests to web-platform-tests.

BUG=588956

Review-Url: https://codereview.chromium.org/2121613002
Cr-Commit-Position: refs/heads/master@{#403890}
9 files changed