Added implementation of three classes in BBR,with unit-tests.

webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h

Index: webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
diff --git a/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h b/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
index a4d8d5ef6378394a128da20a865f9d78752c90f3..77069024ee3af3e57b7ec0d51eaffc2eb1e46477 100644
--- a/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
+++ b/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
@@ -59,13 +59,15 @@ class BbrBweSender : public BweSender {
   void TryExitingStartup();
   void TryExitingDrain(int64_t now_ms);
   void EnterProbeBw(int64_t now_ms);
-  void EnterProbeRtt(int64_t now_ms);
   void TryUpdatingCyclePhase(int64_t now_ms);
-  void TryEnteringProbeRtt(int64_t now_ms);
-  void TryExitingProbeRtt(int64_t now_ms);
+  void TryEnteringProbeRtt(int64_t now_ms, bool min_rtt_expired);
+  void TryExitingProbeRtt(int64_t now_ms, int64_t round, bool min_rtt_expired);
+  size_t TargetCongestionWindow(float gain);
   Clock* const clock_;
   Mode mode_;
   std::unique_ptr<MaxBandwidthFilter> max_bandwidth_filter_;
+  std::unique_ptr<MinRttFilter> min_rtt_filter_;
+  std::unique_ptr<CongestionWindow> congestion_window_;
   uint64_t round_count_;
   uint64_t last_packet_sent_;
   uint64_t round_trip_end_;
@@ -75,6 +77,12 @@ class BbrBweSender : public BweSender {
   // If optimal bandwidth has been discovered and reached, (for example after
   // Startup mode) set this variable to true.
   bool full_bandwidth_reached_;
+  int64_t cycle_start_time_ms_;
+  int64_t cycle_index_;
+  size_t prior_in_flight_;
+  int64_t probe_rtt_start_time_ms_;
+  int64_t minimum_congestion_window_start_time_ms_;
+  int64_t minimum_congestion_window_start_round_;
 };
 
 class BbrBweReceiver : public BweReceiver {