Probing: Add support for exponential startup probing

webrtc/modules/pacing/paced_sender.h

Index: webrtc/modules/pacing/paced_sender.h
diff --git a/webrtc/modules/pacing/paced_sender.h b/webrtc/modules/pacing/paced_sender.h
index c904d4b6b77d1db50dcd23a7ba41e921651d5052..6d2e3c131b44cd828271a04d35554c3ae0bc9fb4 100644
--- a/webrtc/modules/pacing/paced_sender.h
+++ b/webrtc/modules/pacing/paced_sender.h
@@ -15,6 +15,7 @@
 #include <memory>
 #include <set>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
@@ -87,7 +88,7 @@ class PacedSender : public Module, public RtpPacketSender {
   // |bitrate_bps| is our estimate of what we are allowed to send on average.
   // We will pace out bursts of packets at a bitrate of
   // |bitrate_bps| * kDefaultPaceMultiplier.
-  virtual void SetEstimatedBitrate(uint32_t bitrate_bps);
+  virtual void SetEstimatedBitrate(int bitrate_bps);
 
   // Sets the minimum send bitrate and maximum padding bitrate requested by send
   // streams.
@@ -128,6 +129,8 @@ class PacedSender : public Module, public RtpPacketSender {
   // Process any pending packets in the queue(s).
   void Process() override;
 
+  bool IsExpectingProbingResults() const;
+
  private:
   // Updates the number of bytes that can be sent for the next time interval.
   void UpdateBytesPerInterval(int64_t delta_time_in_ms)
@@ -156,10 +159,10 @@ class PacedSender : public Module, public RtpPacketSender {
   std::unique_ptr<BitrateProber> prober_ GUARDED_BY(critsect_);
   // Actual configured bitrates (media_budget_ may temporarily be higher in
   // order to meet pace time constraint).
-  uint32_t estimated_bitrate_bps_ GUARDED_BY(critsect_);
-  uint32_t min_send_bitrate_kbps_ GUARDED_BY(critsect_);
-  uint32_t max_padding_bitrate_kbps_ GUARDED_BY(critsect_);
-  uint32_t pacing_bitrate_kbps_ GUARDED_BY(critsect_);
+  int estimated_bitrate_bps_ GUARDED_BY(critsect_);
+  int min_send_bitrate_kbps_ GUARDED_BY(critsect_);
+  int max_padding_bitrate_kbps_ GUARDED_BY(critsect_);
+  int pacing_bitrate_kbps_ GUARDED_BY(critsect_);
 
   int64_t time_last_update_us_ GUARDED_BY(critsect_);