Add range insertion for base::flat_tree

base/containers/flat_map.h

 // Copyright 2017 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.
 
 #ifndef BASE_CONTAINERS_FLAT_MAP_H_
 #define BASE_CONTAINERS_FLAT_MAP_H_
 
 #include <utility>
 
 #include "base/containers/flat_tree.h"
@@ skipping 80 matching lines @@
 //   const_reverse_iterator crbegin() const;
 //   reverse_iterator       rend();
 //   const_reverse_iterator rend() const;
 //   const_reverse_iterator crend() const;
 //
 // Insert and accessor functions:
 //   Mapped&              operator[](const Key&);
 //   Mapped&              operator[](Key&&);
 //   pair<iterator, bool> insert(const pair<Key, Mapped>&);
 //   pair<iterator, bool> insert(pair<Key, Mapped>&&);
+//   void                 insert(InputIterator first, InputIterator last,
+//                               FlatContainerDupes);
 //   pair<iterator, bool> emplace(Args&&...);
 //   iterator             emplace_hint(const_iterator, Args&&...);
 //
 // Erase functions:
 //   iterator erase(const_iterator);
 //   iterator erase(const_iterator first, const_iterator& last);
 //   size_t   erase(const Key& key)
 //
 // Comparators (see std::map documentation).
 //   key_compare   key_comp() const;
@@ skipping 186 matching lines @@
 // General operations.
 
 template <class Key, class Mapped, class Compare>
 void flat_map<Key, Mapped, Compare>::swap(flat_map& other) {
   tree::swap(other);
 }
 
 }  // namespace base
 
 #endif  // BASE_CONTAINERS_FLAT_MAP_H_