Update from https://crrev.com/311076

net/quic/quic_flags.cc

Index: net/quic/quic_flags.cc
diff --git a/net/quic/quic_flags.cc b/net/quic/quic_flags.cc
index 3146a583bb4b8cbf872500fec02d939d52ac56e4..d7c54b135319d7c90b2c1f620306797bb0f211c1 100644
--- a/net/quic/quic_flags.cc
+++ b/net/quic/quic_flags.cc
@@ -4,14 +4,6 @@
 
 #include "net/quic/quic_flags.h"
 
-// TODO(rtenneti): Remove this.
-// Do not flip this flag until the flakiness of the
-// net/tools/quic/end_to_end_test is fixed.
-// If true, then QUIC connections will track the retransmission history of a
-// packet so that an ack of a previous transmission will ack the data of all
-// other transmissions.
-bool FLAGS_track_retransmission_history = false;
-
 bool FLAGS_quic_allow_oversized_packets_for_test = false;
 
 // When true, the use time based loss detection instead of nack.
@@ -37,7 +29,7 @@ bool FLAGS_quic_use_bbr_congestion_control = false;
 bool FLAGS_quic_allow_bbr = false;
 
 // If true, truncate QUIC connection IDs if the client requests it.
-bool FLAGS_allow_truncated_connection_ids_for_quic = false;
+bool FLAGS_allow_truncated_connection_ids_for_quic = true;
 
 // Do not flip this flag.  jokulik plans more testing and additional monitoring
 // before the flag can go the auto-flip process.
@@ -76,3 +68,6 @@ bool FLAGS_quic_empty_data_no_fin_early_return = true;
 // If true, if min RTT and/or SRTT have not yet been set then initial RTT is
 // used to initialize them in a call to QuicConnection::GetStats.
 bool FLAGS_quic_use_initial_rtt_for_stats = true;
+
+// If true, uses the last sent packet for the RTO timer instead of the earliest.
+bool FLAGS_quic_rto_uses_last_sent = true;