I just noticed that you probably can't use currentTime here... I assume that currentTime doesn't get updated until fastSeek completes, does it?  And of course a fastSeek doesn't to to exactly the time that is specified, so just updating the time to dom.player.duration * pos will be close but not competely accurate. 

Since we pause while dragging, however, we can't just rely on timeUpdated() to update this text.  Maybe you could set an event handler for 'seeked' events and call timeUpdated or updateVideoControlSlider as the event handler for that. 

Or, just use dom.player.duration * pos for now and file a followup bug to investigate further.