Awesome overview! I wonder, when you introduce the that = this pattern, doesn't that become a global variable because you aren't defining a local variable with var?
that = this
Yea basically, with SPDY you can respond to a request for an HTML resource with not only the HTML, but also other assets the browser needs to render that HTML (css, js, images). That way the browser doesn't have the increased latency involved in opening up extra TCP connections to the server to get those assets.