Mojo C++ bindings: switch the existing usage of StructTraits to use the new data view interface.

mojo/public/cpp/bindings/lib/array_serialization.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 MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_
 
 #include <stddef.h>
 #include <string.h>  // For |memcpy()|.
 
@@ skipping 372 matching lines @@
         Impl::SerializeElements(input, buf, result, validate_params, context);
       *output = result;
     } else {
       *output = nullptr;
     }
   }
 
   static bool Deserialize(Data* input,
                           UserType* output,
                           SerializationContext* context) {
-    if (input)
-      return Impl::DeserializeElements(input, output, context);
-    Traits::SetToNull(*output);
-    return true;
+    if (!input)
+      return CallSetToNullIfExists<Traits>(output);
+    return Impl::DeserializeElements(input, output, context);
   }
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_