Convert video-duration*, video-error* and video-load* tests to testharness.js
Cleaning up video-duration*, video-error* and video-load* 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
Committed:
https://crrev.com/cbfa87316823945f92843462c7643e7720d8f623
Cr-Commit-Position: refs/heads/master@{#400908}