Called when the chunk is complete. The BytesWritten property must be accurate after this returns.
Cancellation token.
Optional context data that will be persisted and passed into the next call of FileSystem.ContinueResumableUploadAsync(string fileName, byte[] state, System.Threading.CancellationToken cancellationToken) or FileSystem.CompleteResumableUploadAsync(string fileName, byte[] state, System.Threading.CancellationToken cancellationToken).