Along with sending the SCUP message, this CL includes small fixes which

net/quic/quic_sent_packet_manager.cc

Index: net/quic/quic_sent_packet_manager.cc
diff --git a/net/quic/quic_sent_packet_manager.cc b/net/quic/quic_sent_packet_manager.cc
index f233d8ba7bd327959c4c512e24d4164fab4b7d4b..a0ce684fe7f9d848c5a4427630254d1f77a5af94 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -87,7 +87,8 @@ QuicSentPacketManager::QuicSentPacketManager(
       consecutive_crypto_retransmission_count_(0),
       pending_tlp_transmission_(false),
       max_tail_loss_probes_(kDefaultMaxTailLossProbes),
-      using_pacing_(false) {
+      using_pacing_(false),
+      handshake_confirmed_(false) {
 }
 
 QuicSentPacketManager::~QuicSentPacketManager() {
@@ -606,7 +607,9 @@ bool QuicSentPacketManager::MaybeRetransmitTailLossProbe() {
     if (!it->second.in_flight || frames == NULL) {
       continue;
     }
-    DCHECK_NE(IS_HANDSHAKE, frames->HasCryptoHandshake());
+    if (!handshake_confirmed_) {
+      DCHECK_NE(IS_HANDSHAKE, frames->HasCryptoHandshake());
+    }
     MarkForRetransmission(sequence_number, TLP_RETRANSMISSION);
     return true;
   }
@@ -652,7 +655,7 @@ void QuicSentPacketManager::RetransmitAllPackets() {
 QuicSentPacketManager::RetransmissionTimeoutMode
     QuicSentPacketManager::GetRetransmissionMode() const {
   DCHECK(unacked_packets_.HasInFlightPackets());
-  if (unacked_packets_.HasPendingCryptoPackets()) {
+  if (!handshake_confirmed_ && unacked_packets_.HasPendingCryptoPackets()) {
     return HANDSHAKE_MODE;
   }
   if (loss_algorithm_->GetLossTimeout() != QuicTime::Zero()) {