Open the testcase, use tab to switch focus to the video (first element), hit "end", then "home. Video will start playing. Per the spec, the video starts paused, so it should not start playing in this situation. I suspect the code that deals with video ended in an unpaused state is causing the video to start playing when seeking to the end of the media.
Once the video starts playing, if you seek a second time, the video is paused after seeking.
Created attachment 562631 [details] [diff] [review] Fix Respect the state of the paused attribute after seeking.
Created attachment 563286 [details] [diff] [review] Adds mochitest