The families of two University of Oregon students are offering a reward of up to $1,000 for information leading to the arrest and conviction of the person who tossed a rock from an Interstate 5 overpass. The rock was thrown Monday at 10:40 p.m. from the Isadore Road overpass at Milepost 146 and crashed through the windshield of a vehicle driven by Molly Grabill, 20, a sophomore from Poway, Calif. The rock hit Grabill in the face, leading to a crash that injured her and a passenger, sophomore Chris Brewer, 19, of Vista, Calif. Brewer was treated and released at …