Use overloaded operators with QuicTime for addition, subtraction and scalar

net/quic/congestion_control/tcp_cubic_sender_base.cc

Index: net/quic/congestion_control/tcp_cubic_sender_base.cc
diff --git a/net/quic/congestion_control/tcp_cubic_sender_base.cc b/net/quic/congestion_control/tcp_cubic_sender_base.cc
index 9ab49e92f03c07f51784ab2c00200b82cdd86676..539eadce7247057f39c7165452f0993b9f2c87d1 100644
--- a/net/quic/congestion_control/tcp_cubic_sender_base.cc
+++ b/net/quic/congestion_control/tcp_cubic_sender_base.cc
@@ -243,8 +243,7 @@ QuicTime::Delta TcpCubicSenderBase::RetransmissionDelay() const {
   if (rtt_stats_->smoothed_rtt().IsZero()) {
     return QuicTime::Delta::Zero();
   }
-  return rtt_stats_->smoothed_rtt().Add(
-      rtt_stats_->mean_deviation().Multiply(4));
+  return rtt_stats_->smoothed_rtt() + 4 * rtt_stats_->mean_deviation();
 }
 
 bool TcpCubicSenderBase::InSlowStart() const {