Remove base::underlying_type, replace uses with std::underlying_type

components/prefs/pref_value_store.h

 // Copyright (c) 2012 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 COMPONENTS_PREFS_PREF_VALUE_STORE_H_
 #define COMPONENTS_PREFS_PREF_VALUE_STORE_H_
 
 #include <map>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/values.h"
 #include "components/prefs/base_prefs_export.h"
 #include "components/prefs/pref_store.h"
 
 class PrefNotifier;
@@ skipping 236 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(PrefValueStore);
 };
 
 namespace std {
 
 template <>
 struct hash<PrefValueStore::PrefStoreType> {
   size_t operator()(PrefValueStore::PrefStoreType type) const {
     return std::hash<
-        base::underlying_type<PrefValueStore::PrefStoreType>::type>()(type);
+        std::underlying_type<PrefValueStore::PrefStoreType>::type>()(type);
   }
 };
 
 }  // namespace std
 
 #endif  // COMPONENTS_PREFS_PREF_VALUE_STORE_H_