Walt Disney Studios is marking milestone after milestone.For the first time in its history, Disney has broken the $4 billion mark at the worldwide box office. It previously reached a record high in mid November when “ Thor: The Dark World ” hammered past the $3.791 billion set in 2010.Thanks to “ Iron Man 3 ,” Disney became in July the first studio this year to reach $1 billion in the domestic Bo (for the eight consecutive year). It grossed $2 billion in the worldwide box office, for the fourth year in a row, this August.“Frozen” opened in theaters nationwide Wednesday and “ Saving Mr. Banks ” hits select theaters on Dec. 13 (expanding wide a week later) so the studio is sure to hit several more high notes in the new year. Meanwhile, “ Thor: The Dark World ” has grossed over $559 million in one month.