Show appropriately sized video sources first.

When executing the <video> tags, browsers generally go for the
first source element that they can play. Currently we were ordering
them in ascending order by bitrate. This meant 160p was the first
choice. This seems rather wrong.

Instead order them by ( has a height > player height, smallest bitrate )
This should remove too small transcodes from showing up first, while
still prioritizing the smaller files.

Last of all, this changes the uasort call to be a usort call. I don't
know why this was trying to preserve numeric index keys, but that
doesn't really make sense.

See bug 66143 comment 20.

Change-Id: I6f3316477175634a338efc16a866c7cad0dfc9b3
Merge "Show appropriately sized video sources first."