Answer: Thranduil
As shown in the beginning of the movie, the great dwarf kingdom of Erebor was visited by Thranduil, the Elven King who, as fans of "LOTR" also know, is also the father of Legolas, who did not make an appearance in the first Hobbit movie.
Elrond, while mentioning that he knew Thror when he ruled under the mountain, did not say how or when he'd met him.
Linder is actually the Elf who met the Company when they first arrived at Rivendell after using the Secret Pass to escape the Orcs.