After watching the clip you may be wonder why Gonchar still get penalized, and why Toronto does not get its penalty shot? It's all explained in the NHL rulebook under section 78.6.
Any penalties signaled during the period of time between the apparent goal and the next stoppage of play shall be assessed in the normal manner, except when a minor penalty is to be assessed to the team scored upon, and is therefore nullified by the scoring of the goal. If an infraction happens after the first stoppage of play following an apparent goal (infraction after the whistle) by either team, it is assessed and served in the normal manner regardless as to the decision rendered by the Video Goal Judge.
Only ONE goal may be awarded during a single stoppage in play. Because Toronto could have scored a goal on the penalty shot -- the same stoppage as Gonchar's goal -- that would have obviously been more than one goal on a single stoppage. It's also because of that rule that if Ponikarovsky had scored on his initial breakaway that goal would have been erased from the scoreboard.