Improving flat containers interface.

base/containers/flat_set.h

Index: base/containers/flat_set.h
diff --git a/base/containers/flat_set.h b/base/containers/flat_set.h
index d51dd2678335927485fd61e7bfeb5e4c2920e62f..7531942cf0e9ad6f06cb5684e47d16c53edf4994 100644
--- a/base/containers/flat_set.h
+++ b/base/containers/flat_set.h
@@ -5,9 +5,8 @@
 #ifndef BASE_CONTAINERS_FLAT_SET_H_
 #define BASE_CONTAINERS_FLAT_SET_H_
 
-#include <functional>
-
 #include "base/containers/flat_tree.h"
+#include "base/template_util.h"
 
 namespace base {
 
@@ -23,6 +22,7 @@ namespace base {
 //  - Low overhead, especially for smaller sets.
 //  - Performance is good for more workloads than you might expect (see
 //    overview link above).
+//  - Supports C++14 set interface.
 //
 // CONS
 //
@@ -82,31 +82,32 @@ namespace base {
 //   const_reverse_iterator crend() const;
 //
 // Insert and accessor functions:
-//   pair<iterator, bool> insert(const Key&);
-//   pair<iterator, bool> insert(Key&&);
+//   pair<iterator, bool> insert(const key_type&);
+//   pair<iterator, bool> insert(key_type&&);
 //   void                 insert(InputIterator first, InputIterator last,
 //                               FlatContainerDupes);
 //   pair<iterator, bool> emplace(Args&&...);
 //   iterator             emplace_hint(const_iterator, Args&&...);
 //
 // Erase functions:
+//   iterator erase(iterator);
 //   iterator erase(const_iterator);
 //   iterator erase(const_iterator first, const_iterator& last);
-//   size_t   erase(const Key& key)
+//   template <typename K> size_t erase(const K& key)
 //
 // Comparators (see std::set documentation).
 //   key_compare   key_comp() const;
 //   value_compare value_comp() const;
 //
 // Search functions:
-//   size_t                   count(const Key&) const;
-//   iterator                 find(const Key&);
-//   const_iterator           find(const Key&) const;
-//   pair<iterator, iterator> equal_range(Key&)
-//   iterator                 lower_bound(const Key&);
-//   const_iterator           lower_bound(const Key&) const;
-//   iterator                 upper_bound(const Key&);
-//   const_iterator           upper_bound(const Key&) const;
+//   template <typename K> size_t                   count(const K&) const;
+//   template <typename K> iterator                 find(const K&);
+//   template <typename K> const_iterator           find(const K&) const;
+//   template <typename K> pair<iterator, iterator> equal_range(K&)
+//   template <typename K> iterator                 lower_bound(const K&);
+//   template <typename K> const_iterator           lower_bound(const K&) const;
+//   template <typename K> iterator                 upper_bound(const K&);
+//   template <typename K> const_iterator           upper_bound(const K&) const;
 //
 // General functions:
 //   void swap(flat_set&&)
@@ -119,7 +120,7 @@ namespace base {
 //   bool operator>=(const flat_set&, const flat_set);
 //   bool operator<=(const flat_set&, const flat_set);
 //
-template <class Key, class Compare = std::less<Key>>
+template <class Key, class Compare = ::base::less>
 using flat_set = typename ::base::internal::flat_tree<
     Key,
     Key,