The first request of the session from Chromium to QUIC data saver proxy currently takes at least 1-RTT. This is because the properties of the QUIC data saver server are not persisted on the disk.
The plan is to add the data saver QUIC server to the list of QUIC supported servers at startup in net::QuicStreamFactory class. That will enable Chromium to use 0-RTT even for the first request to the proxy.
Comment 1 by tbansal@chromium.org
, Oct 24 2016