In The Hobbit: The Desolation of Smaug, Thranduil

angrily tells Thorin not to speak of dragon fire, then reveals a vision of half his face burned away.

The conversation implies that Thranduil has been in battle with a dragon. Considering that he leads a Silvan kingdom far to the east and south of what was once Beleriand and Angband, and there is no record of Smaug having visited the Woodland Realm, when and how could Thranduil have experienced dragon fire?