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

webrtc/modules/congestion_controller/probe_controller.cc

Index: webrtc/modules/congestion_controller/probe_controller.cc
diff --git a/webrtc/modules/congestion_controller/probe_controller.cc b/webrtc/modules/congestion_controller/probe_controller.cc
index 52897eef369066460455130f06e9c3c88ef097d9..91340aa430acbe883f9aa671977287b45ac92329 100644
--- a/webrtc/modules/congestion_controller/probe_controller.cc
+++ b/webrtc/modules/congestion_controller/probe_controller.cc
@@ -59,6 +59,7 @@ void ProbeController::SetBitrates(int64_t min_bitrate_bps,
 
   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;
   }
@@ -212,7 +213,7 @@ void ProbeController::Process() {
   // 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;
@@ -227,6 +228,7 @@ void ProbeController::InitiateProbing(
     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) {