Remove base::is_trivially_destructible and use the standard library.

base/optional.h

 // Copyright 2016 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_OPTIONAL_H_
 #define BASE_OPTIONAL_H_
 
 #include <type_traits>
 
 #include "base/logging.h"
-#include "base/template_util.h"
 
 namespace base {
 
 // Specification:
 // http://en.cppreference.com/w/cpp/utility/optional/in_place_t
 struct in_place_t {};
 
 // Specification:
 // http://en.cppreference.com/w/cpp/utility/optional/nullopt_t
 struct nullopt_t {
   constexpr explicit nullopt_t(int) {}
 };
 
 // Specification:
 // http://en.cppreference.com/w/cpp/utility/optional/in_place
 constexpr in_place_t in_place = {};
 
 // Specification:
 // http://en.cppreference.com/w/cpp/utility/optional/nullopt
 constexpr nullopt_t nullopt(0);
 
 namespace internal {
 
-template <typename T, bool = base::is_trivially_destructible<T>::value>
+template <typename T, bool = std::is_trivially_destructible<T>::value>
 struct OptionalStorage {
   // Initializing |empty_| here instead of using default member initializing
   // to avoid errors in g++ 4.8.
   constexpr OptionalStorage() : empty_('\0') {}
 
   constexpr explicit OptionalStorage(const T& value)
       : is_null_(false), value_(value) {}
 
   // TODO(alshabalin): Can't use 'constexpr' with std::move until C++14.
   explicit OptionalStorage(T&& value)
@@ skipping 451 matching lines @@
 template <class T>
 struct hash<base::Optional<T>> {
   size_t operator()(const base::Optional<T>& opt) const {
     return opt == base::nullopt ? 0 : std::hash<T>()(*opt);
   }
 };
 
 }  // namespace std
 
 #endif  // BASE_OPTIONAL_H_