Ignore zero bitrate updates in the UMA BWE stats as they represent network being down and would bia…

webrtc/call/call.cc

Index: webrtc/call/call.cc
diff --git a/webrtc/call/call.cc b/webrtc/call/call.cc
index 51e0cceac98d84b8eb87774232b54075087d5228..fa2d1e7e782d977d65de8a64f5c49a56a31683c5 100644
--- a/webrtc/call/call.cc
+++ b/webrtc/call/call.cc
@@ -710,7 +710,9 @@ void Call::OnNetworkChanged(uint32_t target_bitrate_bps, uint8_t fraction_loss,
   bitrate_allocator_->OnNetworkChanged(target_bitrate_bps, fraction_loss,
                                        rtt_ms);
 
-  {
+  // Ignore updates where the bitrate is zero because the aggregate network
+  // state is down.
+  if (target_bitrate_bps > 0) {
     rtc::CritScope lock(&bitrate_crit_);
     // We only update these stats if we have send streams, and assume that
     // OnNetworkChanged is called roughly with a fixed frequency.