Adds QUIC_VERSION_24 which uses SPDY/4 header compression instead of SPDY/3.

net/quic/quic_session.cc

Index: net/quic/quic_session.cc
diff --git a/net/quic/quic_session.cc b/net/quic/quic_session.cc
index bddc18ef2e8b28203e1a842c1dc0788030adbca0..dc6cdcf5f0e05d5c6b210229b6056423b3af06e3 100644
--- a/net/quic/quic_session.cc
+++ b/net/quic/quic_session.cc
@@ -236,6 +236,10 @@ void QuicSession::OnConnectionClosed(QuicErrorCode error, bool from_peer) {
   }
 }
 
+void QuicSession::OnSuccessfulVersionNegotiation(const QuicVersion& version) {
+  headers_stream_->OnSuccessfulVersionNegotiation(version);
+}
+
 void QuicSession::OnWindowUpdateFrames(
     const vector<QuicWindowUpdateFrame>& frames) {
   bool connection_window_updated = false;