Rectify our use of std::nullptr_t, inclusions of <stddef.h>/<cstddef>.

mojo/public/cpp/bindings/array.h

 // Copyright 2013 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 MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_
 
+#include <stddef.h>
 #include <string.h>
 
 #include <algorithm>
 #include <cstddef>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "mojo/public/cpp/bindings/lib/array_internal.h"
 #include "mojo/public/cpp/bindings/lib/bindings_internal.h"
@@ skipping 13 matching lines @@
   using Traits = internal::ArrayTraits<T, internal::IsMoveOnlyType<T>::value>;
   using ForwardType = typename Traits::ForwardType;
 
   typedef internal::Array_Data<typename internal::WrapperTraits<T>::DataType>
       Data_;
 
   // Constructs a new array that is null.
   Array() : is_null_(true) {}
 
   // Makes null arrays implicitly constructible from |nullptr|.
-  Array(decltype(nullptr)) : is_null_(true) {}
+  Array(std::nullptr_t) : is_null_(true) {}
 
   ~Array() {}
 
   // Moves the contents of |other| into this array.
   Array(Array&& other) : is_null_(true) { Take(&other); }
   Array& operator=(Array&& other) {
     Take(&other);
     return *this;
   }
 
@@ skipping 253 matching lines @@
       for (size_t i = 0; i < input.size(); ++i)
         result.insert(TypeConverter<E, T>::Convert(input[i]));
     }
     return result;
   }
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_