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

third_party/base/numerics/safe_math.h

Index: third_party/base/numerics/safe_math.h
diff --git a/third_party/base/numerics/safe_math.h b/third_party/base/numerics/safe_math.h
index 9540e83321a8f0dba960828e5831f46a821d29d2..013af1eb60972fa7ebed4ba8cf004cdda5eb1c1a 100644
--- a/third_party/base/numerics/safe_math.h
+++ b/third_party/base/numerics/safe_math.h
@@ -166,15 +166,15 @@ class CheckedNumeric {
   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;
   }