Revalidating
A cache-aware source that fires onTileRevalidated — off the render thread — after a stale tile has been re-downloaded and written through (the stale-while-revalidate refresh). The render layer wires this to drop the tile's cached texture / coverage entry and request a redraw, so the freshly-cached bytes appear on-screen without waiting for the next reload.
Coordinates are the source's native (z, x, y) — slippy (z, column, row) for image tile sources, (matrix ordinal, column, row) for elevation source factories.
Implemented by CachedTileSource and the GeoPackage elevation source factory. The callback must marshal any cache mutation onto the render thread itself (the render caches aren't synchronized); WorldWind.requestRedraw is the safe cross-thread signal.