Protect UpdateRTT from negative send deltas

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 9b1e9470024b79bdb210d4aa2ac1535925713778..7b25b6c6d373268a76a2085e4f20b056d859e41d 100644
--- a/net/quic/congestion_control/rtt_stats.cc
+++ b/net/quic/congestion_control/rtt_stats.cc
@@ -53,9 +53,10 @@ void RttStats::ExpireSmoothedMetrics() {
 void RttStats::UpdateRtt(QuicTime::Delta send_delta,
                          QuicTime::Delta ack_delay,
                          QuicTime now) {
-  if (send_delta.IsInfinite() || send_delta.IsZero()) {
-    DVLOG(1) << "Ignoring measured send_delta, because it's "
-             << (send_delta.IsZero() ? "Zero" : "Infinite");
+  if (send_delta.IsInfinite() || send_delta <= QuicTime::Delta::Zero()) {
+    LOG(WARNING) << "Ignoring measured send_delta, because it's is "
+                 << "either infinite, zero, or negative.  send_delta = "
+                 << send_delta.ToMicroseconds();
     return;
   }