Don't initiate perodic probing if we don't have a bandwidth estimate.

webrtc/modules/pacing/bitrate_prober.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 68 matching lines @@
       packet_size >=
           std::min<size_t>(RecommendedMinProbeSize(), kMinProbePacketSize)) {
     // Send next probe right away.
     next_probe_time_ms_ = -1;
     probing_state_ = ProbingState::kActive;
   }
 }
 
 void BitrateProber::CreateProbeCluster(int bitrate_bps, int64_t now_ms) {
   RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
+  RTC_DCHECK_GT(bitrate_bps, 0);
   while (!clusters_.empty() &&
          now_ms - clusters_.front().time_created_ms > kProbeClusterTimeoutMs) {
     clusters_.pop();
   }
 
   ProbeCluster cluster;
   cluster.time_created_ms = now_ms;
   cluster.pace_info.probe_cluster_min_probes = kMinProbePacketsSent;
   cluster.pace_info.probe_cluster_min_bytes =
       bitrate_bps * kMinProbeDurationMs / 8000;
@@ skipping 45 matching lines @@
       ResetState(now_ms);
       return -1;
     }
   }
 
   return std::max(time_until_probe_ms, 0);
 }
 
 PacedPacketInfo BitrateProber::CurrentCluster() const {
   RTC_DCHECK(!clusters_.empty());
-  RTC_DCHECK(ProbingState::kActive == probing_state_);
+  RTC_DCHECK(probing_state_ == ProbingState::kActive);
   return clusters_.front().pace_info;
 }
 
 // Probe size is recommended based on the probe bitrate required. We choose
 // a minimum of twice |kMinProbeDeltaMs| interval to allow scheduling to be
 // feasible.
 size_t BitrateProber::RecommendedMinProbeSize() const {
   RTC_DCHECK(!clusters_.empty());
   return clusters_.front().pace_info.send_bitrate_bps * 2 * kMinProbeDeltaMs /
          (8 * 1000);
 }
 
 void BitrateProber::ProbeSent(int64_t now_ms, size_t bytes) {
   RTC_DCHECK(probing_state_ == ProbingState::kActive);
   RTC_DCHECK_GT(bytes, 0);
 
   if (!clusters_.empty()) {
     ProbeCluster* cluster = &clusters_.front();
     if (cluster->sent_probes == 0) {
       RTC_DCHECK_EQ(cluster->time_started_ms, -1);
       cluster->time_started_ms = now_ms;
     }
     cluster->sent_bytes += static_cast<int>(bytes);
     cluster->sent_probes += 1;
-    next_probe_time_ms_ = GetNextProbeTime(clusters_.front());
+    next_probe_time_ms_ = GetNextProbeTime(*cluster);
     if (cluster->sent_bytes >= cluster->pace_info.probe_cluster_min_bytes &&
         cluster->sent_probes >= cluster->pace_info.probe_cluster_min_probes) {
       clusters_.pop();
     }
     if (clusters_.empty())
       probing_state_ = ProbingState::kSuspended;
   }
 }
 
 int64_t BitrateProber::GetNextProbeTime(const ProbeCluster& cluster) {
   RTC_CHECK_GT(cluster.pace_info.send_bitrate_bps, 0);
   RTC_CHECK_GE(cluster.time_started_ms, 0);
 
   // Compute the time delta from the cluster start to ensure probe bitrate stays
   // close to the target bitrate. Result is in milliseconds.
   int64_t delta_ms =
       (8000ll * cluster.sent_bytes + cluster.pace_info.send_bitrate_bps / 2) /
       cluster.pace_info.send_bitrate_bps;
   return cluster.time_started_ms + delta_ms;
 }
 
 
 }  // namespace webrtc