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diff --git a/third_party/libwebrtc/api/video/frame_buffer.h b/third_party/libwebrtc/api/video/frame_buffer.h
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+++ b/third_party/libwebrtc/api/video/frame_buffer.h
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+/*
+ *  Copyright (c) 2021 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 API_VIDEO_FRAME_BUFFER_H_
+#define API_VIDEO_FRAME_BUFFER_H_
+
+#include <map>
+#include <memory>
+#include <utility>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/types/optional.h"
+#include "api/field_trials_view.h"
+#include "api/video/encoded_frame.h"
+#include "modules/video_coding/utility/decoded_frames_history.h"
+
+namespace webrtc {
+// The high level idea of the FrameBuffer is to order frames received from the
+// network into a decodable stream. Frames are order by frame ID, and grouped
+// into temporal units by timestamp. A temporal unit is decodable after all
+// referenced frames outside the unit has been decoded, and a temporal unit is
+// continuous if all referenced frames are directly or indirectly decodable.
+// The FrameBuffer is thread-unsafe.
+class FrameBuffer {
+ public:
+  struct DecodabilityInfo {
+    uint32_t next_rtp_timestamp;
+    uint32_t last_rtp_timestamp;
+  };
+
+  // The `max_size` determines the maximum number of frames the buffer will
+  // store, and max_decode_history determines how far back (by frame ID) the
+  // buffer will store if a frame was decoded or not.
+  FrameBuffer(int max_size,
+              int max_decode_history,
+              // TODO(hta): remove field trials!
+              const FieldTrialsView& field_trials);
+  FrameBuffer(const FrameBuffer&) = delete;
+  FrameBuffer& operator=(const FrameBuffer&) = delete;
+  ~FrameBuffer() = default;
+
+  // Inserted frames may only reference backwards, and must have no duplicate
+  // references. Frame insertion will fail if `frame` is a duplicate, has
+  // already been decoded, invalid, or if the buffer is full and the frame is
+  // not a keyframe. Returns true if the frame was successfully inserted.
+  bool InsertFrame(std::unique_ptr<EncodedFrame> frame);
+
+  // Mark all frames belonging to the next decodable temporal unit as decoded
+  // and returns them.
+  absl::InlinedVector<std::unique_ptr<EncodedFrame>, 4>
+  ExtractNextDecodableTemporalUnit();
+
+  // Drop all frames in the next decodable unit.
+  void DropNextDecodableTemporalUnit();
+
+  absl::optional<int64_t> LastContinuousFrameId() const;
+  absl::optional<int64_t> LastContinuousTemporalUnitFrameId() const;
+  absl::optional<DecodabilityInfo> DecodableTemporalUnitsInfo() const;
+
+  int GetTotalNumberOfContinuousTemporalUnits() const;
+  int GetTotalNumberOfDroppedFrames() const;
+  int GetTotalNumberOfDiscardedPackets() const;
+  size_t CurrentSize() const;
+
+ private:
+  struct FrameInfo {
+    std::unique_ptr<EncodedFrame> encoded_frame;
+    bool continuous = false;
+  };
+
+  using FrameMap = std::map<int64_t, FrameInfo>;
+  using FrameIterator = FrameMap::iterator;
+
+  struct TemporalUnit {
+    // Both first and last are inclusive.
+    FrameIterator first_frame;
+    FrameIterator last_frame;
+  };
+
+  bool IsContinuous(const FrameIterator& it) const;
+  void PropagateContinuity(const FrameIterator& frame_it);
+  void FindNextAndLastDecodableTemporalUnit();
+  void Clear();
+  void UpdateDroppedFramesAndDiscardedPackets(FrameIterator begin_it,
+                                              FrameIterator end_it);
+
+  const bool legacy_frame_id_jump_behavior_;
+  const size_t max_size_;
+  FrameMap frames_;
+  absl::optional<TemporalUnit> next_decodable_temporal_unit_;
+  absl::optional<DecodabilityInfo> decodable_temporal_units_info_;
+  absl::optional<int64_t> last_continuous_frame_id_;
+  absl::optional<int64_t> last_continuous_temporal_unit_frame_id_;
+  video_coding::DecodedFramesHistory decoded_frame_history_;
+
+  int num_continuous_temporal_units_ = 0;
+  int num_dropped_frames_ = 0;
+  int num_discarded_packets_ = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // API_VIDEO_FRAME_BUFFER_H_