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

webrtc/modules/congestion_controller/probe_controller.cc

 /*
  *  Copyright (c) 2016 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 41 matching lines @@
   Reset();
 }
 
 void ProbeController::SetBitrates(int64_t min_bitrate_bps,
                                   int64_t start_bitrate_bps,
                                   int64_t max_bitrate_bps) {
   rtc::CritScope cs(&critsect_);
 
   if (start_bitrate_bps > 0)  {
     start_bitrate_bps_ = start_bitrate_bps;
+    estimated_bitrate_bps_ = start_bitrate_bps;
   } else if (start_bitrate_bps_ == 0) {
     start_bitrate_bps_ = min_bitrate_bps;
   }
 
   // The reason we use the variable |old_max_bitrate_pbs| is because we
   // need to set |max_bitrate_bps_| before we call InitiateProbing.
   int64_t old_max_bitrate_bps = max_bitrate_bps_;
   max_bitrate_bps_ = max_bitrate_bps;
 
   switch (state_) {
@@ skipping 133 matching lines @@
       min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
     }
   }
 
   if (state_ != State::kProbingComplete || !enable_periodic_alr_probing_)
     return;
 
   // Probe bandwidth periodically when in ALR state.
   rtc::Optional<int64_t> alr_start_time =
       pacer_->GetApplicationLimitedRegionStartTime();
-  if (alr_start_time) {
+  if (alr_start_time && estimated_bitrate_bps_ > 0) {
     int64_t next_probe_time_ms =
         std::max(*alr_start_time, time_last_probing_initiated_ms_) +
         kAlrPeriodicProbingIntervalMs;
     if (now_ms >= next_probe_time_ms) {
       InitiateProbing(now_ms, {estimated_bitrate_bps_ * 2}, true);
     }
   }
 }
 
 void ProbeController::InitiateProbing(
     int64_t now_ms,
     std::initializer_list<int64_t> bitrates_to_probe,
     bool probe_further) {
   for (int64_t bitrate : bitrates_to_probe) {
+    RTC_DCHECK_GT(bitrate, 0);
     int64_t max_probe_bitrate_bps =
         max_bitrate_bps_ > 0 ? max_bitrate_bps_ : kDefaultMaxProbingBitrateBps;
     if (bitrate > max_probe_bitrate_bps) {
       bitrate = max_probe_bitrate_bps;
       probe_further = false;
     }
     pacer_->CreateProbeCluster(rtc::dchecked_cast<int>(bitrate));
   }
   time_last_probing_initiated_ms_ = now_ms;
   if (probe_further) {
     state_ = State::kWaitingForProbingResult;
     min_bitrate_to_probe_further_bps_ =
         (*(bitrates_to_probe.end() - 1)) * kRepeatedProbeMinPercentage / 100;
   } else {
     state_ = State::kProbingComplete;
     min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
   }
 }
 
 }  // namespace webrtc