Store net::ProxyServer in HttpResponseInfo object.

Store net::ProxyServer in HttpResponseInfo instead of
net::HostPortPair. This makes it possible for the net
consumers to determine the proxy scheme used for a given
request (e.g., QUIC vs. HTTPS)

BUG=646197

Review-Url: https://codereview.chromium.org/2334623003
Cr-Commit-Position: refs/heads/master@{#423567}
24 files changed