Protect against the divide by zero error in QuicBandwidth::TransferTime.

net/quic/quic_bandwidth.cc

Index: net/quic/quic_bandwidth.cc
diff --git a/net/quic/quic_bandwidth.cc b/net/quic/quic_bandwidth.cc
index cdd2986b1675faf51d72c66f2cb284bce6711f4a..dbce39d354908a30c431dc7b5776ea795181f07c 100644
--- a/net/quic/quic_bandwidth.cc
+++ b/net/quic/quic_bandwidth.cc
@@ -100,6 +100,9 @@ QuicBandwidth QuicBandwidth::Scale(float scale_factor) const {
 }
 
 QuicTime::Delta QuicBandwidth::TransferTime(QuicByteCount bytes) const {
+  if (bits_per_second_ == 0) {
+    return QuicTime::Delta::Zero();
+  }
   return QuicTime::Delta::FromMicroseconds(
       bytes * 8 * base::Time::kMicrosecondsPerSecond / bits_per_second_);
 }