"In the current APIs, when HttpURLConnection is called, it calls into
HttpClient directly to make a connection. This is a problem for us
because the file may have already been downloaded by plugin/webstart
before, and the current APIs will always go ahead and download the file
again. This also means that until the file is downloaded intentionally
through our special APIs in plugin/webstart, any arbitrary HTTP/HTTPS
calls will always bypass our caching code, which is not good.

	What we want is to have another layer between HttpURLConnection and
HttpClient:

	HttpURLConnection -> Caching Layer -> HttpClient

	By default, the caching layer probably doesn't do anything other than
forwarding the call to HttpClient. With this additional layer, we can
leverage our own plugin/webstart cache more easily and we can be assure
that all the connections will go through our caching code." -- Stanley Ho