Remove warning about std::map::emplace

base/containers/mru_cache.h

 // Copyright (c) 2011 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 file contains a template for a Most Recently Used cache that allows
 // constant-time access to items using a key, but easy identification of the
 // least-recently-used items for removal.  Each key can only be associated with
 // one payload item at a time.
 //
 // The key object will be stored twice, so it should support efficient copying.
@@ skipping 79 matching lines @@
     if (index_iter != index_.end()) {
       // Erase the reference to it. The index reference will be replaced in the
       // code below.
       Erase(index_iter->second);
     } else if (max_size_ != NO_AUTO_EVICT) {
       // New item is being inserted which might make it larger than the maximum
       // size: kick the oldest thing out if necessary.
       ShrinkToSize(max_size_ - 1);
     }
 
-    ordering_.push_front(value_type(key, std::forward<Payload>(payload)));
-    index_.insert(std::make_pair(key, ordering_.begin()));
+    ordering_.emplace_front(key, std::forward<Payload>(payload));
+    index_.emplace(key, ordering_.begin());

[jdoerrie, 2017/04/25 11:33:47]

While |index_|'s type is a template parameter, it defaults to std::map. The
corresponding unit tests cover this case, thus this should be sufficient to
check the feature's availability.

     return ordering_.begin();
   }
 
   // Retrieves the contents of the given key, or end() if not found. This method
   // has the side effect of moving the requested item to the front of the
   // recency list.
   iterator Get(const KeyType& key) {
     typename KeyIndex::iterator index_iter = index_.find(key);
     if (index_iter == index_.end())
       return end();
@@ skipping 135 matching lines @@
       : ParentType(max_size) {}
   virtual ~HashingMRUCache() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HashingMRUCache);
 };
 
 }  // namespace base
 
 #endif  // BASE_CONTAINERS_MRU_CACHE_H_