platformViewBackdrop property

Whether the bar floats over a native platform view — an iOS map, say.

Forwarded to every capsule this bar draws, in-route and pinned alike, so the two look identical across the hand-over. The glass shader reads a captured backdrop the platform view is never part of, so without this a capsule over one has nothing to refract; the flag routes it to the live BackdropFilter instead, as GlassButton.platformViewBackdrop does.