Mojo C++ bindings: introduce an optional array to store transferred interface IDs in messages.

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 270 matching lines @@
                       MojomTypeCategory::HANDLE |
                       MojomTypeCategory::INTERFACE |
                       MojomTypeCategory::INTERFACE_REQUEST>::value>::type> {
   using UserType = typename std::remove_const<MaybeConstUserType>::type;
   using Data = typename MojomTypeTraits<MojomType>::Data;
   using Element = typename MojomType::Element;
   using Traits = ArrayTraits<UserType>;
 
   static size_t GetSerializedSize(UserTypeIterator* input,
                                   SerializationContext* context) {
-    return sizeof(Data) +
-           Align(input->GetSize() * sizeof(typename Data::Element));
+    size_t element_count = input->GetSize();
+    if (BelongsTo<Element,
+                  MojomTypeCategory::ASSOCIATED_INTERFACE |
+                      MojomTypeCategory::ASSOCIATED_INTERFACE_REQUEST>::value) {
+      for (size_t i = 0; i < element_count; ++i) {
+        typename UserTypeIterator::GetNextResult next = input->GetNext();
+        size_t size = PrepareToSerialize<Element>(next, context);
+        DCHECK_EQ(size, 0u);
+      }
+    }
+    return sizeof(Data) + Align(element_count * sizeof(typename Data::Element));
   }
 
   static void SerializeElements(UserTypeIterator* input,
                                 Buffer* buf,
                                 Data* output,
                                 const ContainerValidateParams* validate_params,
                                 SerializationContext* context) {
     DCHECK(!validate_params->element_validate_params)
         << "Handle or interface type should not have array validate params";
 
@@ skipping 234 matching lines @@
     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_