OK, I found his patch. I had to take him off my ignore list before looking at his message before it would show me the attachment.
He whacked downloadFile - but I whacked it even more severely when I souped up image caching.
Basically, he is always asking for the file from the remote server, but he's saying "send a not modified if it is not modified after the date I gave you" - the date being the modification date of the locally cached file. And since my (more recent than his patch) code sets the modification date to the date that came with the file, that's reasonable enough.
The result of the "setIfModifiedSince" is to add a If-Modified-Since header to the HTTP request, which will result in the remote server either sending a 200 and the file or a 304, which says "use what you have".
I think "smarterCache" is a bad name for the optional third parameter to downloadFile. I'd call it "probeLastModified" or something.
Let me see how I would integrate that into the current version of downloadFile.