How does the "GG" system work in competitive play?

[sadge]

Just curious - who decides exactly when the game is over (usually gg's are called before the throne is taken) and presses the button to end the game? What happens if a player types "GG" by accident or does the "Good game, well played" chat wheel by accident?

[Multi]

In private lobbies like that, if "gg" is said in the all chat, a window pops up that the whole team can see. If anyone clicks it, it cancels it. If nobody cancels it, it makes their team forfeit.