andreasgal/vtt.js — pull request #128 by jespirit (2013-10-06 16:37:14+00:00)
Title: If region already had one child, set appropriate transition styles

From the processing model step 12, substep 2 about a cue that lies within a region, states:

* If region's text track region scroll setting is 'up' and region already has one child, set region's 'transition-property' to 'top' and 'transition-duration' to '0.433s'.