What is this row of pits along the "upper lip" of theropod skulls?
They are called Nutrient Foramen which are innervation of blood vessels and nerves, you see the same thing in reptile and bird skulls (mammals tent to pack it all into one or two large openings). They feed blood vessels and nerves to the gums, lips, and face.

Dinosaurs do seem to have more of them, but size making them more noticable is also a factor. The increase in dinosaurs may be involved with pressure sensitive scales as seen in crocodiles or alternatively something like lips, or both. Here is a great article on them. Paleontologist are hampered here becasue the related animals are birds (who have beaks) and crocodiles (which are entirely scaly). So it is hard to pin down exactly what a dinosaur oral facial anatomy would look like.