Update from chromium https://crrev.com/302282

net/quic/congestion_control/prr_sender.h

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Implements Proportional Rate Reduction (PRR) per RFC 6937.
+
+#ifndef NET_QUIC_CONGESTION_CONTROL_PRR_SENDER_H_
+#define NET_QUIC_CONGESTION_CONTROL_PRR_SENDER_H_
+
+#include "net/quic/quic_bandwidth.h"
+#include "net/quic/quic_time.h"
+
+namespace net {
+
+class NET_EXPORT_PRIVATE PrrSender {
+ public:
+  PrrSender();
+  // OnPacketLost should be called on the first loss that triggers a recovery
+  // period and all other methods in this class should only be called when in
+  // recovery.
+  void OnPacketLost(QuicByteCount bytes_in_flight);
+  void OnPacketSent(QuicByteCount sent_bytes);
+  void OnPacketAcked(QuicByteCount acked_bytes);
+  QuicTime::Delta TimeUntilSend(QuicByteCount congestion_window,
+                                QuicByteCount bytes_in_flight,
+                                QuicPacketCount slowstart_threshold)
+      const;
+
+ private:
+  // Bytes sent and acked since the last loss event.
+  // |bytes_sent_since_loss_| is the same as "prr_out_" in RFC 6937,
+  // and |bytes_delivered_since_loss_| is the same as "prr_delivered_".
+  QuicByteCount bytes_sent_since_loss_;
+  QuicByteCount bytes_delivered_since_loss_;
+  size_t ack_count_since_loss_;
+
+  // The congestion window before the last loss event.
+  QuicByteCount bytes_in_flight_before_loss_;
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_CONGESTION_CONTROL_PRR_SENDER_H_