In cronet.idl for the native API, ERROR_QUIC_PROTOCOL_FAILED has a comment stating: "this exception can be cast to {@link QuicException} for more information".

This isn't meaningful for the C API, which doesn't have exceptions. 

Looks like a copypasta from Java -> native.

[1] https://cs.chromium.org/chromium/src/components/cronet/native/cronet.idl?l=112&rcl=8b620ce0f0349154d485835cd6f9e710073a5e4d