I appreciate the strictly logical argument for classing it as an OG, but I think Aguero will be unlucky if they take the goal off him ... because down the years I can think of many many occasions in football games where a ball has struck the back of a goalkeeper, his foot, his hand, squeezed in at the near post where arguably the ball came off the post for a split-second and then off the keeper into the goal ... and 99% of them were given to the striker anyway.
You also see several goals a season where a keeper goes down to smother a shot and ends up pushing the ball against his own thigh or foot and from there it rolls back across the line. Shots sometimes bounce off his elbow as he dives but then spin back, etc etc. But they are always given to the striker, because after all the goalie was doing his best, if he hadn't thrown himself at the ball it would have gone in anyway ... so it would seem very harsh to put his name up in lights with a big "O.G." after it.
Also, of course, the striker wants the goal and the goalie does not want the OG. IMO, "OG"s should really be saved for proper cock-ups, not unavoidable deflections whilst making a genuine attempt to save the shot.
Most goalies go their whole careers without a single "OG" and if you applied the rule as strictly as some people on here would like to, I don't think that would happen ... I think every goalie would have half a dozen career own-goals if you counted any time the ball was not strictly heading into the goal when it last touched any part of his body.
So I think Aguero should be given the goal.