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.
+ *
+ */
+
+#include "webrtc/modules/remote_bitrate_estimator/test/estimators/congestion_window.h"
+
+#include <algorithm>
+
+#include "webrtc/modules/remote_bitrate_estimator/test/estimators/bbr.h"
+
+namespace webrtc {
+namespace testing {
+namespace bwe {
+const int64_t kStartingCongestionWindow = 6000;

[philipel, 2017/07/06 12:15:14]

Put const values inside an anonymous namespace.

[philipel, 2017/07/06 12:15:14]

Add comments about what these values mean and where you got them from.

[gnish1, 2017/07/07 13:43:33]

Done.

[gnish1, 2017/07/07 13:43:34]

Done.

[gnish1, 2017/07/07 13:43:34]

Done.

[gnish1, 2017/07/07 13:43:34]

Done.

+const int64_t kMinimumCongestionWindow = 5840;
+
+CongestionWindow::CongestionWindow() : data_inflight_(0) {}
+
+CongestionWindow::~CongestionWindow() {}
+
+int64_t CongestionWindow::GetCongestionWindow(BbrBweSender::Mode mode,
+                                              int64_t bandwidth_estimate,
+                                              int64_t min_rtt,
+                                              float gain,
+                                              size_t bytes_acked,
+                                              int multiplier) {
+  if (mode == 3)

[philipel, 2017/07/06 12:15:15]

Use enum, not '3'.

[gnish1, 2017/07/07 13:43:34]

Done.

+    return kMinimumCongestionWindow;
+  return GetTargetCongestionWindow(bandwidth_estimate, min_rtt, gain) +
+         multiplier * bytes_acked;
+}
+
+void CongestionWindow::PacketSent(size_t sent_packet_size) {
+  data_inflight_ += sent_packet_size;
+}
+
+void CongestionWindow::AckReceived(size_t received_packet_size) {
+  data_inflight_ -= received_packet_size;
+}
+
+int64_t CongestionWindow::GetTargetCongestionWindow(int64_t bandwidth_estimate,
+                                                    int64_t min_rtt,
+                                                    float gain) {
+  int64_t bdp = min_rtt * bandwidth_estimate;
+  int64_t congestion_window = bdp * gain;
+  if (!congestion_window) {

[philipel, 2017/07/06 12:15:14]

How/why can the congestion window be 0? Add comment.

[philipel, 2017/07/06 12:15:14]

remove {}

[gnish1, 2017/07/07 13:43:34]

Done.

[gnish1, 2017/07/07 13:43:34]

Done.

+    congestion_window = gain * kStartingCongestionWindow;
+  }
+  return std::max(congestion_window, kMinimumCongestionWindow);
+}
+}  // namespace bwe
+}  // namespace testing
+}  // namespace webrtc