Ask HN: How does Google Maps transfer '0 byte' images on Street View?

I was reading the answer to this question http://stackoverflow.com/questions/8072921/chrome-dev-tools-size-vs-content on Stack Overflow about 'Size' vs 'Content' on the Network tab of Chrome, and the accepted answer said: ... "Size" is the number of bytes on the wire, and "content" is the actual size of the resource. A number of things can make them different, including: * Being served from cache (small or 0 "size") * GZip encoding (smaller size than content) * Request/Response headers, including cookies (larger size than content) * Redirects or authentication requests ... So I was a little surprised when I was checking the network tab on a typical street view page on Google maps and observed that the size of almost every tile (JPEG) was 0 but it wasn't being served from a local cache nor was it gzipped. Here's what I see (note 6th column, Size/Content): http://i.imgur.com/VpENUSC.png How is this happening, how can the file they transfer be 0 on the wire but definitely have content (as indicated) without caching or gzipping? I'd love some more clarification if I'm misunderstanding something obvious. Thanks!