Switch from nonstd::unique_ptr to std::unique_ptr.

third_party/base/numerics/safe_math.h

 // Copyright 2014 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 PDFIUM_THIRD_PARTY_BASE_SAFE_MATH_H_
 #define PDFIUM_THIRD_PARTY_BASE_SAFE_MATH_H_
 
 #include "safe_math_impl.h"
 
 namespace pdfium {
@@ skipping 148 matching lines @@
     *this -= 1;
     return value;
   }
 
   // These static methods behave like a convenience cast operator targeting
   // the desired CheckedNumeric type. As an optimization, a reference is
   // returned when Src is the same type as T.
   template <typename Src>
   static CheckedNumeric<T> cast(
       Src u,
-      typename enable_if<std::numeric_limits<Src>::is_specialized, int>::type =
-          0) {
+      typename std::enable_if<std::numeric_limits<Src>::is_specialized,
+                              int>::type = 0) {
     return u;
   }
 
   template <typename Src>
   static CheckedNumeric<T> cast(
       const CheckedNumeric<Src>& u,
-      typename enable_if<!is_same<Src, T>::value, int>::type = 0) {
+      typename std::enable_if<!std::is_same<Src, T>::value, int>::type = 0) {
     return u;
   }
 
   static const CheckedNumeric<T>& cast(const CheckedNumeric<T>& u) { return u; }
 
  private:
   CheckedNumericState<T> state_;
 };
 
 // This is the boilerplate for the standard arithmetic operator overloads. A
@@ skipping 75 matching lines @@
 #undef BASE_NUMERIC_ARITHMETIC_OPERATORS
 
 }  // namespace internal
 
 using internal::CheckedNumeric;
 
 }  // namespace base
 }  // namespace pdfium
 
 #endif  // PDFIUM_THIRD_PARTY_BASE_SAFE_MATH_H_