Try to clay bar it. Maybe (hopefully) it's just a contaminant that will lift right off. I had something on one of my exterior mirrors that looked like a very deep haze. Regular glass cleaner wouldn't get it off, but clay bar did.
2014 IS 350 F-Sport RWD
Nebula Gray / Light Gray - Navi / ML / BSM / VGRS / Tint / Xpel Ultimate