[giow] (3) Make adding a cue, or changing its timings, work when the video is paused.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=16920
Affected topics: HTML, Video Text Tracks, Video and Audio

git-svn-id: http://svn.whatwg.org/webapps@7835 340c8d12-0b0e-0410-8428-c7bf67bfef74