Fixes two div by zero bugs in QUIC's BBR pacing code that caused server

net/quic/congestion_control/rtt_stats.cc

Index: net/quic/congestion_control/rtt_stats.cc
diff --git a/net/quic/congestion_control/rtt_stats.cc b/net/quic/congestion_control/rtt_stats.cc
index b03686d747e6621102e0dd7e11d125fdf261e528..d5f48697ef45f40b9fe0f183ad5b12a8374567d3 100644
--- a/net/quic/congestion_control/rtt_stats.cc
+++ b/net/quic/congestion_control/rtt_stats.cc
@@ -64,11 +64,11 @@ void RttStats::UpdateRtt(QuicTime::Delta send_delta,
   }
 
   if (rtt_sample.IsInfinite() || rtt_sample.IsZero()) {
-    DVLOG(1) << "Ignoring rtt, because it's "
-             << (rtt_sample.IsZero() ? "Zero" : "Infinite");
+    LOG(WARNING) << "Ignoring rtt, because it's "
+                 << (rtt_sample.IsZero() ? "Zero" : "Infinite");
     return;
   }
-  // RTT can't be negative.
+  // RTT can't be non-positive.
   DCHECK_LT(0, rtt_sample.ToMicroseconds());
 
   latest_rtt_ = rtt_sample;
@@ -138,4 +138,11 @@ QuicTime::Delta RttStats::SmoothedRtt() const {
   return smoothed_rtt_;
 }
 
+QuicTime::Delta RttStats::MinRtt() const {
+  if (!HasUpdates()) {
+    return QuicTime::Delta::FromMicroseconds(initial_rtt_us_);
+  }
+  return min_rtt_;
+}
+
 }  // namespace net