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 06e403b2d3bb922518bf73384aa8f3d47a37f773..a4d8d5ef6378394a128da20a865f9d78752c90f3 100644
--- a/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
+++ b/webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h
@@ -57,12 +57,12 @@ class BbrBweSender : public BweSender {
   void EnterStartup();
   bool UpdateBandwidthAndMinRtt();
   void TryExitingStartup();
-  void TryExitingDrain(int64_t now);
-  void EnterProbeBw(int64_t now);
-  void EnterProbeRtt(int64_t now);
-  void TryUpdatingCyclePhase(int64_t now);
-  void TryEnteringProbeRtt(int64_t now);
-  void TryExitingProbeRtt(int64_t now);
+  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);
   Clock* const clock_;
   Mode mode_;
   std::unique_ptr<MaxBandwidthFilter> max_bandwidth_filter_;