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diff --git a/third_party/libwebrtc/p2p/base/stun_dictionary.h b/third_party/libwebrtc/p2p/base/stun_dictionary.h
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+++ b/third_party/libwebrtc/p2p/base/stun_dictionary.h
@@ -0,0 +1,204 @@
+/*
+ *  Copyright 2020 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 P2P_BASE_STUN_DICTIONARY_H_
+#define P2P_BASE_STUN_DICTIONARY_H_
+
+#include <deque>
+#include <map>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "api/rtc_error.h"
+#include "api/transport/stun.h"
+
+namespace cricket {
+
+// A StunDictionaryView is a dictionary of StunAttributes.
+//   - the StunAttributes can be read using the |Get|-methods.
+//   - the dictionary is updated by using the |ApplyDelta|-method.
+//
+// A StunDictionaryWriter is used to create |delta|s for the |ApplyDelta|-method
+// - It keeps track of which updates has been applied at StunDictionaryView.
+// - It optionally keeps a local StunDictionaryView contains modification made
+// `locally`
+//
+// A pair StunDictionaryView(A)/StunDictionaryWriter(B) are linked so that
+// modifications to B is transfered to A using the STUN_ATTR_GOOG_DELTA
+// (StunByteStringAttribute) and the modification is ack:ed using
+// STUN_ATTR_GOOG_DELTA_ACK (StunUInt64Attribute).
+//
+// Note:
+// 1) It is possible to update one StunDictionaryView from multiple writers,
+// but this only works of the different writers write disjoint keys (which
+// is not checked/enforced by these classes).
+// 2) The opposite, one writer updating multiple StunDictionaryView, is not
+// possible.
+class StunDictionaryView {
+ public:
+  // A reserved key used to transport the version number
+  static constexpr uint16_t kVersionKey = 0xFFFF;
+
+  // A magic number used when transporting deltas.
+  static constexpr uint16_t kDeltaMagic = 0x7788;
+
+  // The version number for the delta format.
+  static constexpr uint16_t kDeltaVersion = 0x1;
+
+  // Gets the desired attribute value, or NULL if no such attribute type exists.
+  // The pointer returned is guaranteed to be valid until ApplyDelta is called.
+  const StunAddressAttribute* GetAddress(int key) const;
+  const StunUInt32Attribute* GetUInt32(int key) const;
+  const StunUInt64Attribute* GetUInt64(int key) const;
+  const StunByteStringAttribute* GetByteString(int key) const;
+  const StunUInt16ListAttribute* GetUInt16List(int key) const;
+
+  bool empty() const { return attrs_.empty(); }
+  size_t size() const { return attrs_.size(); }
+  int bytes_stored() const { return bytes_stored_; }
+  void set_max_bytes_stored(int max_bytes_stored) {
+    max_bytes_stored_ = max_bytes_stored;
+  }
+
+  // Apply a delta and return
+  // a pair with
+  // - StunUInt64Attribute to ack the |delta|.
+  // - vector of keys that was modified.
+  webrtc::RTCErrorOr<
+      std::pair<std::unique_ptr<StunUInt64Attribute>, std::vector<uint16_t>>>
+  ApplyDelta(const StunByteStringAttribute& delta);
+
+ private:
+  friend class StunDictionaryWriter;
+
+  const StunAttribute* GetOrNull(
+      int key,
+      absl::optional<StunAttributeValueType> = absl::nullopt) const;
+  size_t GetLength(int key) const;
+  static webrtc::RTCErrorOr<
+      std::pair<uint64_t, std::deque<std::unique_ptr<StunAttribute>>>>
+  ParseDelta(const StunByteStringAttribute& delta);
+
+  std::map<uint16_t, std::unique_ptr<StunAttribute>> attrs_;
+  std::map<uint16_t, uint64_t> version_per_key_;
+
+  int max_bytes_stored_ = 16384;
+  int bytes_stored_ = 0;
+};
+
+class StunDictionaryWriter {
+ public:
+  StunDictionaryWriter() {
+    dictionary_ = std::make_unique<StunDictionaryView>();
+  }
+  explicit StunDictionaryWriter(
+      std::unique_ptr<StunDictionaryView> dictionary) {
+    dictionary_ = std::move(dictionary);
+  }
+
+  // A pending modification.
+  template <typename T>
+  class Modification {
+   public:
+    ~Modification() { commit(); }
+
+    T* operator->() { return attr_.get(); }
+
+    void abort() { attr_ = nullptr; }
+    void commit() {
+      if (attr_) {
+        writer_->Set(std::move(attr_));
+      }
+    }
+
+   private:
+    friend class StunDictionaryWriter;
+    Modification(StunDictionaryWriter* writer, std::unique_ptr<T> attr)
+        : writer_(writer), attr_(std::move(attr)) {}
+    StunDictionaryWriter* writer_;
+    std::unique_ptr<T> attr_;
+
+    Modification(const Modification<T>&) =
+        delete;  // not copyable (but movable).
+    Modification& operator=(Modification<T>&) =
+        delete;  // not copyable (but movable).
+  };
+
+  // Record a modification.
+  Modification<StunAddressAttribute> SetAddress(int key) {
+    return Modification<StunAddressAttribute>(
+        this, StunAttribute::CreateAddress(key));
+  }
+  Modification<StunUInt32Attribute> SetUInt32(int key) {
+    return Modification<StunUInt32Attribute>(this,
+                                             StunAttribute::CreateUInt32(key));
+  }
+  Modification<StunUInt64Attribute> SetUInt64(int key) {
+    return Modification<StunUInt64Attribute>(this,
+                                             StunAttribute::CreateUInt64(key));
+  }
+  Modification<StunByteStringAttribute> SetByteString(int key) {
+    return Modification<StunByteStringAttribute>(
+        this, StunAttribute::CreateByteString(key));
+  }
+  Modification<StunUInt16ListAttribute> SetUInt16List(int key) {
+    return Modification<StunUInt16ListAttribute>(
+        this, StunAttribute::CreateUInt16ListAttribute(key));
+  }
+
+  // Delete a key.
+  void Delete(int key);
+
+  // Check if a key has a pending change (i.e a change
+  // that has not been acked).
+  bool Pending(int key) const;
+
+  // Return number of of pending modifications.
+  int Pending() const;
+
+  // Create an StunByteStringAttribute containing the pending (e.g not ack:ed)
+  // modifications.
+  std::unique_ptr<StunByteStringAttribute> CreateDelta();
+
+  // Apply an delta ack.
+  void ApplyDeltaAck(const StunUInt64Attribute&);
+
+  // Return pointer to (optional) StunDictionaryView.
+  const StunDictionaryView* dictionary() { return dictionary_.get(); }
+  const StunDictionaryView* operator->() { return dictionary_.get(); }
+
+  // Disable writer,
+  // i.e CreateDelta always return null, and no modifications are made.
+  // This is called if remote peer does not support GOOG_DELTA.
+  void Disable();
+  bool disabled() const { return disabled_; }
+
+ private:
+  void Set(std::unique_ptr<StunAttribute> attr);
+
+  bool disabled_ = false;
+
+  // version of modification.
+  int64_t version_ = 1;
+
+  // (optional) StunDictionaryView.
+  std::unique_ptr<StunDictionaryView> dictionary_;
+
+  // sorted list of changes that has not been yet been ack:ed.
+  std::vector<std::pair<uint64_t, const StunAttribute*>> pending_;
+
+  // tombstones, i.e values that has been deleted but not yet acked.
+  std::map<uint16_t, std::unique_ptr<StunAttribute>> tombstones_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_STUN_DICTIONARY_H_