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

webrtc/modules/remote_bitrate_estimator/test/estimators/congestion_window.cc

 /*
  *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  *
  */
@@ skipping 15 matching lines @@
 const int kStartingCongestionWindow = 6000;
 // Size of congestion window while in PROBE_RTT mode, suggested by BBR's source
 // code of QUIC's implementation.
 const int kMinimumCongestionWindow = 5840;
 }  // namespace
 
 CongestionWindow::CongestionWindow() : data_inflight_bytes_(0) {}
 
 CongestionWindow::~CongestionWindow() {}
 
-int CongestionWindow::GetCongestionWindow(
-    BbrBweSender::Mode mode,
-    int64_t bandwidth_estimate_bytes_per_ms,
-    int64_t min_rtt_ms,
-    float gain) {
+int CongestionWindow::GetCongestionWindow(BbrBweSender::Mode mode,
+                                          int64_t bandwidth_estimate_bps,
+                                          rtc::Optional<int64_t> min_rtt_ms,
+                                          float gain) {
   if (mode == BbrBweSender::PROBE_RTT)
     return kMinimumCongestionWindow;
-  return GetTargetCongestionWindow(bandwidth_estimate_bytes_per_ms, min_rtt_ms,
-                                   gain);
+  return GetTargetCongestionWindow(bandwidth_estimate_bps, min_rtt_ms, gain);
 }
 
 void CongestionWindow::PacketSent(size_t sent_packet_size_bytes) {
   data_inflight_bytes_ += sent_packet_size_bytes;
 }
 
 void CongestionWindow::AckReceived(size_t received_packet_size_bytes) {
   data_inflight_bytes_ -= received_packet_size_bytes;
 }
 
 int CongestionWindow::GetTargetCongestionWindow(
-    int64_t bandwidth_estimate_bytes_per_ms,
-    int64_t min_rtt_ms,
+    int64_t bandwidth_estimate_bps,
+    rtc::Optional<int64_t> min_rtt_ms,
     float gain) {
-  int bdp = min_rtt_ms * bandwidth_estimate_bytes_per_ms;
+  int bdp = *min_rtt_ms * bandwidth_estimate_bps;
   int congestion_window = bdp * gain;
   // Congestion window could be zero in rare cases, when either no bandwidth
   // estimate is available, or path's min_rtt value is zero.
   if (!congestion_window)
     congestion_window = gain * kStartingCongestionWindow;
   return std::max(congestion_window, kMinimumCongestionWindow);
 }
 }  // namespace bwe
 }  // namespace testing
 }  // namespace webrtc