Warner Bros. has zeroed in on “Line of Sight,” buying F. Scott Frazier’s thriller spec preemptively and setting it up with Silver Pictures.Plot details are under wraps, but the project’s described as a high-concept thriller with gritty, street-level action and suspense. The studio made the purchase late Friday. Joel Silver and Andrew Rona will produce and Alex Heineman will exec produce. The script is based on an original idea by Silver Pictures VP Heineman, who also originated teen comedy “Project X.” Frazier also wrote “Embassy” and “The Numbers Station.” Sarah Schechter and Chantal Nong will oversee the project for WB. Frazier’s repped by WME and H2F.