Function optional_device_features 

pub fn optional_device_features(adapter: &Adapter) -> Features

The optional device features the renderer exploits when the adapter offers them: pipeline caching (see pipeline_disk_cache), the timestamp queries behind CRANPOSE_GPU_PASS_TIMING, and, on a GPU that shares the host’s memory, vertex and uniform buffers the CPU writes directly, so a frame’s uploads need no copy. Every platform’s request_device passes this so a profiling toggle never needs a rebuilt binary; intersecting with the adapter’s own features keeps the request valid on adapters without them.