from Kerry Fraser of TSN,

There is no question that Reilly Smith was guilty of charging when he crashed into Roberto Luongo after the puck entered the net. The goal would stand since the puck crossed the line prior to the infraction but a minor penalty should have been assessed to Smith.

Let me attempt to explain why the referee might not have reacted to the contact on Luongo and therefore did not call a penalty. From the ref's position (behind the goal line, on the same side of the net that Smith approached 'Lou') the referee was focused on multiple elements of this bang-bang play.

First, there was potential for a penalty shot to be called if a foul from behind had resulted once Christopher Tanev gave chase from his opposite-side defensive position. Tanev attacked from a back-side angle and made stick-to-stick contact with Smith just as the shot was being taken from outside the goal crease. Tanev then slid behind Smith making very light physical contact with the back of the Bruin player.

continued and watch the goal below...

To answer my own question, I think it was a good no-call.