diff --git a/common/simple_linked_hash_map.h b/common/simple_linked_hash_map.h
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+// Copyright (c) 2019 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.
+
+// This is a simplistic insertion-ordered map.  It behaves similarly to an STL
+// map, but only implements a small subset of the map's methods.  Internally, we
+// just keep a map and a list going in parallel.
+//
+// This class provides no thread safety guarantees, beyond what you would
+// normally see with std::list.
+//
+// Iterators point into the list and should be stable in the face of
+// mutations, except for an iterator pointing to an element that was just
+// deleted.
+
+#ifndef QUICHE_COMMON_SIMPLE_LINKED_HASH_MAP_H_
+#define QUICHE_COMMON_SIMPLE_LINKED_HASH_MAP_H_
+
+#include <list>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "net/third_party/quiche/src/common/platform/api/quiche_unordered_containers.h"
+
+namespace quiche {
+
+// This holds a list of pair<Key, Value> items.  This list is what gets
+// traversed, and it's iterators from this list that we return from
+// begin/end/find.
+//
+// We also keep a set<list::iterator> for find.  Since std::list is a
+// doubly-linked list, the iterators should remain stable.
+
+template <class Key, class Value, class Hash = std::hash<Key>>
+class SimpleLinkedHashMap {
+ private:
+  typedef std::list<std::pair<Key, Value>> ListType;
+  typedef QuicheUnorderedMap<Key, typename ListType::iterator, Hash> MapType;
+
+ public:
+  typedef typename ListType::iterator iterator;
+  typedef typename ListType::reverse_iterator reverse_iterator;
+  typedef typename ListType::const_iterator const_iterator;
+  typedef typename ListType::const_reverse_iterator const_reverse_iterator;
+  typedef typename MapType::key_type key_type;
+  typedef typename ListType::value_type value_type;
+  typedef typename ListType::size_type size_type;
+
+  SimpleLinkedHashMap() = default;
+  explicit SimpleLinkedHashMap(size_type bucket_count) : map_(bucket_count) {}
+
+  SimpleLinkedHashMap(const SimpleLinkedHashMap& other) = delete;
+  SimpleLinkedHashMap& operator=(const SimpleLinkedHashMap& other) = delete;
+  SimpleLinkedHashMap(SimpleLinkedHashMap&& other) = default;
+  SimpleLinkedHashMap& operator=(SimpleLinkedHashMap&& other) = default;
+
+  // Returns an iterator to the first (insertion-ordered) element.  Like a map,
+  // this can be dereferenced to a pair<Key, Value>.
+  iterator begin() { return list_.begin(); }
+  const_iterator begin() const { return list_.begin(); }
+
+  // Returns an iterator beyond the last element.
+  iterator end() { return list_.end(); }
+  const_iterator end() const { return list_.end(); }
+
+  // Returns an iterator to the last (insertion-ordered) element.  Like a map,
+  // this can be dereferenced to a pair<Key, Value>.
+  reverse_iterator rbegin() { return list_.rbegin(); }
+  const_reverse_iterator rbegin() const { return list_.rbegin(); }
+
+  // Returns an iterator beyond the first element.
+  reverse_iterator rend() { return list_.rend(); }
+  const_reverse_iterator rend() const { return list_.rend(); }
+
+  // Front and back accessors common to many stl containers.
+
+  // Returns the earliest-inserted element
+  const value_type& front() const { return list_.front(); }
+
+  // Returns the earliest-inserted element.
+  value_type& front() { return list_.front(); }
+
+  // Returns the most-recently-inserted element.
+  const value_type& back() const { return list_.back(); }
+
+  // Returns the most-recently-inserted element.
+  value_type& back() { return list_.back(); }
+
+  // Clears the map of all values.
+  void clear() {
+    map_.clear();
+    list_.clear();
+  }
+
+  // Returns true iff the map is empty.
+  bool empty() const { return list_.empty(); }
+
+  // Removes the first element from the list.
+  void pop_front() { erase(begin()); }
+
+  // Erases values with the provided key.  Returns the number of elements
+  // erased.  In this implementation, this will be 0 or 1.
+  size_type erase(const Key& key) {
+    typename MapType::iterator found = map_.find(key);
+    if (found == map_.end()) {
+      return 0;
+    }
+
+    list_.erase(found->second);
+    map_.erase(found);
+
+    return 1;
+  }
+
+  // Erases the item that 'position' points to. Returns an iterator that points
+  // to the item that comes immediately after the deleted item in the list, or
+  // end().
+  // If the provided iterator is invalid or there is inconsistency between the
+  // map and list, a CHECK() error will occur.
+  iterator erase(iterator position) {
+    typename MapType::iterator found = map_.find(position->first);
+    CHECK(found->second == position)
+        << "Inconsisent iterator for map and list, or the iterator is invalid.";
+
+    map_.erase(found);
+    return list_.erase(position);
+  }
+
+  // Erases all the items in the range [first, last).  Returns an iterator that
+  // points to the item that comes immediately after the last deleted item in
+  // the list, or end().
+  iterator erase(iterator first, iterator last) {
+    while (first != last && first != end()) {
+      first = erase(first);
+    }
+    return first;
+  }
+
+  // Finds the element with the given key.  Returns an iterator to the
+  // value found, or to end() if the value was not found.  Like a map, this
+  // iterator points to a pair<Key, Value>.
+  iterator find(const Key& key) {
+    typename MapType::iterator found = map_.find(key);
+    if (found == map_.end()) {
+      return end();
+    }
+    return found->second;
+  }
+
+  const_iterator find(const Key& key) const {
+    typename MapType::const_iterator found = map_.find(key);
+    if (found == map_.end()) {
+      return end();
+    }
+    return found->second;
+  }
+
+  bool contains(const Key& key) const { return find(key) != end(); }
+
+  // Returns the value mapped to key, or an inserted iterator to that position
+  // in the map.
+  Value& operator[](const key_type& key) {
+    return (*((this->insert(std::make_pair(key, Value()))).first)).second;
+  }
+
+  // Inserts an element into the map
+  std::pair<iterator, bool> insert(const std::pair<Key, Value>& pair) {
+    // First make sure the map doesn't have a key with this value.  If it does,
+    // return a pair with an iterator to it, and false indicating that we
+    // didn't insert anything.
+    typename MapType::iterator found = map_.find(pair.first);
+    if (found != map_.end()) {
+      return std::make_pair(found->second, false);
+    }
+
+    // Otherwise, insert into the list first.
+    list_.push_back(pair);
+
+    // Obtain an iterator to the newly added element.  We do -- instead of -
+    // since list::iterator doesn't implement operator-().
+    typename ListType::iterator last = list_.end();
+    --last;
+
+    CHECK(map_.insert(std::make_pair(pair.first, last)).second)
+        << "Map and list are inconsistent";
+
+    return std::make_pair(last, true);
+  }
+
+  // Inserts an element into the map
+  std::pair<iterator, bool> insert(std::pair<Key, Value>&& pair) {
+    // First make sure the map doesn't have a key with this value.  If it does,
+    // return a pair with an iterator to it, and false indicating that we
+    // didn't insert anything.
+    typename MapType::iterator found = map_.find(pair.first);
+    if (found != map_.end()) {
+      return std::make_pair(found->second, false);
+    }
+
+    // Otherwise, insert into the list first.
+    list_.push_back(std::move(pair));
+
+    // Obtain an iterator to the newly added element.  We do -- instead of -
+    // since list::iterator doesn't implement operator-().
+    typename ListType::iterator last = list_.end();
+    --last;
+
+    CHECK(map_.insert(std::make_pair(pair.first, last)).second)
+        << "Map and list are inconsistent";
+    return std::make_pair(last, true);
+  }
+
+  size_type size() const { return list_.size(); }
+
+  template <typename... Args>
+  std::pair<iterator, bool> emplace(Args&&... args) {
+    ListType node_donor;
+    auto node_pos =
+        node_donor.emplace(node_donor.end(), std::forward<Args>(args)...);
+    const auto& k = node_pos->first;
+    auto ins = map_.insert({k, node_pos});
+    if (!ins.second) {
+      return {ins.first->second, false};
+    }
+    list_.splice(list_.end(), node_donor, node_pos);
+    return {ins.first->second, true};
+  }
+
+  void swap(SimpleLinkedHashMap& other) {
+    map_.swap(other.map_);
+    list_.swap(other.list_);
+  }
+
+ private:
+  // The map component, used for speedy lookups
+  MapType map_;
+
+  // The list component, used for maintaining insertion order
+  ListType list_;
+};
+
+}  // namespace quiche
+
+#endif  // QUICHE_COMMON_SIMPLE_LINKED_HASH_MAP_H_