RICE HILL — Oregon State Police are following up tips in search of the person who threw a rock from an Interstate 5 overpass that crashed through a windshield and injured a University of Oregon student. “It’s my top-priority case right now,” OSP Detective Tom Willis said today. Willis said police have received some anonymous tips from the public and hope for more developments in the next day or two. Police are still asking for the public’s help, he said. Molly Grabill, 20, of Poway, Calif., was driving north on I-5 at 10:40 p.m. Monday when a rock larger than …