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 a0531cc27ec3560b02765d599849123523d68b08..1af34318e9b8c0c818ef666a4fd5c0383995b2f0 100644
--- a/webrtc/modules/congestion_controller/include/congestion_controller.h
+++ b/webrtc/modules/congestion_controller/include/congestion_controller.h
@@ -15,6 +15,7 @@
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/common_types.h"
+#include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/modules/pacing/packet_router.h"
@@ -28,7 +29,6 @@ struct SentPacket;
 
 namespace webrtc {
 
-class BitrateController;
 class Clock;
 class ProcessThread;
 class RateLimiter;
@@ -96,7 +96,12 @@ class CongestionController : public CallStatsObserver, public Module {
   void SetAllocatedSendBitrateLimits(int min_send_bitrate_bps,
                                      int max_padding_bitrate_bps);
 
-  virtual void OnSentPacket(const rtc::SentPacket& sent_packet);
+  void OnSentPacket(const rtc::SentPacket& sent_packet);
+
+  // Called by delay based estimator to report estimated bandwidth.
+  void OnDelayBasedBweChanged(int bitrate_bps);
+  void OnProbingBitrateMeasured(int bitrate_bps);
+  PacedSender::State SenderState();
 
   // Implements CallStatsObserver.
   void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) override;