Line of sight dots on "chasm" map tile
The Chasm room space with the bridge does not have line of sight to the room Crypt or Cave, because it does not have line of sight dots.

From the rule book page 21 (emphasis mine).


  Note that monsters, investigators and feature markers do not block line of sight. Also note that some spaces do not have line of sight dots. A figure in one of these spaces has line of sight to every space in the room (and does not have line of sight to other rooms).