Windshield Leaks

That is a leaded area from the factory. I believe what your problem is that someone replaced the windshield at some point with out using window sealer in the gasket and over time the leaking caused the leaded joints to corrode. I would wire wheel off everything you can and get a better look at it. It may need to be releaded. Rust is your worst enemy. Make sure you use sealer in the gasket channels when reinstalling the windshield, that is what keeps it from leaking.