Ask at the Chrysler parts department for a bottle of "Super Clean". They also have "Total Clean" that works on many things but Super Clean does a better job on tough stuff like tar and tape residue. It will start to dissolve the glue after you just dab it on. It's real good for grease on fabric too. I'm sure the GM dealer's parts department will have similar products but it's the Chrysler names I'm familiar with. You can also ask at the dealer's detail department. Some have separate detail guys. Some farm that out to other companies, and some have those guys in a room attached to the body shop. All they do is clean up cars to make them look like new before they get placed on the sales lot, and right before a new buyer is scheduled to take delivery.
If you clean this yourself, watch out if there's thin grid lines going across the glass for the degogger. Use a chemical that won't cause that copper to crumble, but one that's strong enough so you don't have to scrub very hard.