Adds dynamic setting of FEC group size based on the connection's current

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 b5ca9fe9e51f08f7f93e6fe3aeb4ce2a9643c3d7..9bc0f87f2ac906c371828d8f5c1d1940562ad8fe 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -73,6 +73,7 @@ QuicSentPacketManager::QuicSentPacketManager(bool is_server,
       clock_(clock),
       stats_(stats),
       debug_delegate_(NULL),
+      network_change_visitor_(NULL),
       send_algorithm_(
           SendAlgorithmInterface::Create(clock, &rtt_stats_, type, stats)),
       loss_algorithm_(LossDetectionInterface::Create(loss_type)),
@@ -119,6 +120,10 @@ void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
     loss_algorithm_.reset(LossDetectionInterface::Create(kTime));
   }
   send_algorithm_->SetFromConfig(config, is_server_);
+
+  if (network_change_visitor_ != NULL) {
+    network_change_visitor_->OnCongestionWindowChange(GetCongestionWindow());
+  }
 }
 
 // TODO(ianswett): Combine this method with OnPacketSent once packets are always
@@ -207,12 +212,15 @@ void QuicSentPacketManager::OnIncomingAck(
 
 void QuicSentPacketManager::MaybeInvokeCongestionEvent(
     bool rtt_updated, QuicByteCount bytes_in_flight) {
-  if (rtt_updated || !packets_acked_.empty() ||
-      !packets_lost_.empty()) {
-    send_algorithm_->OnCongestionEvent(
-        rtt_updated, bytes_in_flight, packets_acked_, packets_lost_);
-    packets_acked_.clear();
-    packets_lost_.clear();
+  if (!rtt_updated && packets_acked_.empty() && packets_lost_.empty()) {
+    return;
+  }
+  send_algorithm_->OnCongestionEvent(rtt_updated, bytes_in_flight,
+                                     packets_acked_, packets_lost_);
+  packets_acked_.clear();
+  packets_lost_.clear();
+  if (network_change_visitor_ != NULL) {
+    network_change_visitor_->OnCongestionWindowChange(GetCongestionWindow());
   }
 }
 
@@ -628,6 +636,10 @@ void QuicSentPacketManager::RetransmitAllPackets() {
     }
     ++consecutive_rto_count_;
   }
+
+  if (network_change_visitor_ != NULL) {
+    network_change_visitor_->OnCongestionWindowChange(GetCongestionWindow());
+  }
 }
 
 QuicSentPacketManager::RetransmissionTimeoutMode