This is a handful of GET requests for images. You would need a page to fingerprint. The site could get an IP, likely the user agent. Safe browsing requests are sandboxed from all the other Google cookies.
https://safebrowsing.google.com/safebrowsing/downloads?clien...
Isn't the API key your fingerprint? The key is not shown here, because the author was showing what the requests look like on first run, subsequent requests would contain your unique ID in them.
Not picking on you specifically, I saw several responses saying the same thing.
No, it's a per-application key, so in this case it would be IceWeasel's key.
There's nothing to stop, say, ebay from serving PHP scripts on ICO extension, processing the request as a pageload and then ultimately returning the icon file, but for anything useful to have been gleaned, it would have generated more requests.
Either it did generate more requests and Mozilla didn't honor them (in which case, yay), or it didn't generate more requests (in which case, yay). The former would be slightly preferred as the latter doesn't prevent ebay from later changing their strategy.