r272352 removed the `.track.fill` that was used as a "background" for the slider
for videos that aren't fully loaded and are buffering, that "background" is necessary to indicate where the slider is as the `.track.secondary` only represents what's been buffered not the entire length of the video/slider
Created attachment 419457 [details]
Committed r272438: <https://trac.webkit.org/changeset/272438>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 419457 [details].