Probing: Add support for exponential startup probing

webrtc/modules/bitrate_controller/include/bitrate_controller.h

Index: webrtc/modules/bitrate_controller/include/bitrate_controller.h
diff --git a/webrtc/modules/bitrate_controller/include/bitrate_controller.h b/webrtc/modules/bitrate_controller/include/bitrate_controller.h
index 4c4578adf04fb31c65c81bdd8e4e9fa9081493e2..90b64713907d368f03456c3243f5967b8948b89b 100644
--- a/webrtc/modules/bitrate_controller/include/bitrate_controller.h
+++ b/webrtc/modules/bitrate_controller/include/bitrate_controller.h
@@ -19,6 +19,7 @@
 
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/pacing/paced_sender.h"
+#include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 
 namespace webrtc {
@@ -43,7 +44,7 @@ class BitrateObserver {
   virtual ~BitrateObserver() {}
 };
 
-class BitrateController : public Module {
+class BitrateController : public Module, public RemoteBitrateObserver {
   // This class collects feedback from all streams sent to a peer (via
   // RTCPBandwidthObservers). It does one  aggregated send side bandwidth
   // estimation and divide the available bitrate between all its registered
@@ -77,10 +78,6 @@ class BitrateController : public Module {
                              int min_bitrate_bps,
                              int max_bitrate_bps) = 0;
 
-  virtual void UpdateDelayBasedEstimate(uint32_t bitrate_bps) = 0;
-
-  virtual void UpdateProbeBitrate(uint32_t bitrate_bps) = 0;
-
   // Gets the available payload bandwidth in bits per second. Note that
   // this bandwidth excludes packet headers.
   virtual bool AvailableBandwidth(uint32_t* bandwidth) const = 0;