My 2004 Highlander's windshield has some kind of grid, made up of round holes, around the edges (about 3/4" in) and a larger area around the rear view mirror (about 5" x 7"). What is the purpose of this? (Radio antenna? Glare reduction? etc.) Windshield needs replaced; is it important to have this "grid"?

For everyone's information: I got an answer to this question myself. The pattern on the windshield that I am talking about is known as a "third visor frit", which IS intended for glare reduction. I understand it is a standard feature on these windshields (Highlander, but not sure about other Toyotas).
I learned the answer from Safelite Auto Glass Co. No one at my dealer knew the answer; the best guess they had was something to do with auto-dimming rear view mirror, which is not the case.