Probing: Add support for exponential startup probing

webrtc/modules/congestion_controller/include/congestion_controller.h

Index: webrtc/modules/congestion_controller/include/congestion_controller.h
diff --git a/webrtc/modules/congestion_controller/include/congestion_controller.h b/webrtc/modules/congestion_controller/include/congestion_controller.h
index 57c2c64ff4eb396573e2e478eb2b1896e808443a..e224c38a2b87e3cb734509022bc58e7a82650a92 100644
--- a/webrtc/modules/congestion_controller/include/congestion_controller.h
+++ b/webrtc/modules/congestion_controller/include/congestion_controller.h
@@ -30,6 +30,7 @@ namespace webrtc {
 
 class BitrateController;
 class Clock;
+class ProbeController;
 class ProcessThread;
 class RateLimiter;
 class RemoteBitrateEstimator;
@@ -98,6 +99,11 @@ class CongestionController : public CallStatsObserver, public Module {
 
   virtual void OnSentPacket(const rtc::SentPacket& sent_packet);
 
+  // Called by delay based estimator to report estimated bandwidth.
+  void OnDelayBasedBweChanged(int bitrate_bps);
+  // Called by delay based estimator to report measured probing bitrate.
+  void OnProbeBitrate(int bitrate_bps);
+
   // Implements CallStatsObserver.
   void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) override;
 
@@ -120,12 +126,12 @@ class CongestionController : public CallStatsObserver, public Module {
   const std::unique_ptr<PacedSender> pacer_;
   const std::unique_ptr<RemoteBitrateEstimator> remote_bitrate_estimator_;
   const std::unique_ptr<BitrateController> bitrate_controller_;
+  const std::unique_ptr<ProbeController> probe_controller_;
   const std::unique_ptr<RateLimiter> retransmission_rate_limiter_;
   RemoteEstimatorProxy remote_estimator_proxy_;
   TransportFeedbackAdapter transport_feedback_adapter_;
   int min_bitrate_bps_;
   int max_bitrate_bps_;
-  bool initial_probing_triggered_;
   rtc::CriticalSection critsect_;
   uint32_t last_reported_bitrate_bps_ GUARDED_BY(critsect_);
   uint8_t last_reported_fraction_loss_ GUARDED_BY(critsect_);