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diff --git a/third_party/libwebrtc/modules/pacing/bitrate_prober.h b/third_party/libwebrtc/modules/pacing/bitrate_prober.h
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+/*
+ *  Copyright (c) 2014 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.
+ */
+
+#ifndef MODULES_PACING_BITRATE_PROBER_H_
+#define MODULES_PACING_BITRATE_PROBER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <queue>
+
+#include "api/transport/field_trial_based_config.h"
+#include "api/transport/network_types.h"
+#include "rtc_base/experiments/field_trial_parser.h"
+
+namespace webrtc {
+class RtcEventLog;
+
+struct BitrateProberConfig {
+  explicit BitrateProberConfig(const FieldTrialsView* key_value_config);
+  BitrateProberConfig(const BitrateProberConfig&) = default;
+  BitrateProberConfig& operator=(const BitrateProberConfig&) = default;
+  ~BitrateProberConfig() = default;
+
+  // A minimum interval between probes to allow scheduling to be feasible.
+  FieldTrialParameter<TimeDelta> min_probe_delta;
+  // Maximum amount of time each probe can be delayed.
+  FieldTrialParameter<TimeDelta> max_probe_delay;
+  // This is used to start sending a probe after a large enough packet.
+  // The min packet size is scaled with the bitrate we're probing at.
+  // This defines the max min packet size, meaning that on high bitrates
+  // a packet of at least this size is needed to trigger sending a probe.
+  FieldTrialParameter<DataSize> min_packet_size;
+};
+
+// Note that this class isn't thread-safe by itself and therefore relies
+// on being protected by the caller.
+class BitrateProber {
+ public:
+  explicit BitrateProber(const FieldTrialsView& field_trials);
+  ~BitrateProber() = default;
+
+  void SetEnabled(bool enable);
+
+  // Returns true if the prober is in a probing session, i.e., it currently
+  // wants packets to be sent out according to the time returned by
+  // TimeUntilNextProbe().
+  bool is_probing() const { return probing_state_ == ProbingState::kActive; }
+
+  // Initializes a new probing session if the prober is allowed to probe. Does
+  // not initialize the prober unless the packet size is large enough to probe
+  // with.
+  void OnIncomingPacket(DataSize packet_size);
+
+  // Create a cluster used to probe.
+  void CreateProbeCluster(const ProbeClusterConfig& cluster_config);
+  // Returns the time at which the next probe should be sent to get accurate
+  // probing. If probing is not desired at this time, Timestamp::PlusInfinity()
+  // will be returned.
+  // TODO(bugs.webrtc.org/11780): Remove `now` argument when old mode is gone.
+  Timestamp NextProbeTime(Timestamp now) const;
+
+  // Information about the current probing cluster.
+  absl::optional<PacedPacketInfo> CurrentCluster(Timestamp now);
+
+  // Returns the minimum number of bytes that the prober recommends for
+  // the next probe, or zero if not probing. A probe can consist of multiple
+  // packets that are sent back to back.
+  DataSize RecommendedMinProbeSize() const;
+
+  // Called to report to the prober that a probe has been sent. In case of
+  // multiple packets per probe, this call would be made at the end of sending
+  // the last packet in probe. `size` is the total size of all packets in probe.
+  void ProbeSent(Timestamp now, DataSize size);
+
+ private:
+  enum class ProbingState {
+    // Probing will not be triggered in this state at all times.
+    kDisabled,
+    // Probing is enabled and ready to trigger on the first packet arrival.
+    kInactive,
+    // Probe cluster is filled with the set of data rates to be probed and
+    // probes are being sent.
+    kActive,
+    // Probing is enabled, but currently suspended until an explicit trigger
+    // to start probing again.
+    kSuspended,
+  };
+
+  // A probe cluster consists of a set of probes. Each probe in turn can be
+  // divided into a number of packets to accommodate the MTU on the network.
+  struct ProbeCluster {
+    PacedPacketInfo pace_info;
+
+    int sent_probes = 0;
+    int sent_bytes = 0;
+    Timestamp requested_at = Timestamp::MinusInfinity();
+    Timestamp started_at = Timestamp::MinusInfinity();
+    int retries = 0;
+  };
+
+  Timestamp CalculateNextProbeTime(const ProbeCluster& cluster) const;
+
+  ProbingState probing_state_;
+
+  // Probe bitrate per packet. These are used to compute the delta relative to
+  // the previous probe packet based on the size and time when that packet was
+  // sent.
+  std::queue<ProbeCluster> clusters_;
+
+  // Time the next probe should be sent when in kActive state.
+  Timestamp next_probe_time_;
+
+  BitrateProberConfig config_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_PACING_BITRATE_PROBER_H_