Mojo C++ bindings: Fix bug: array<>, map<> should only initialize elements if they're not null when…

mojo/public/cpp/bindings/lib/map_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_MAP_SERIALIZATION_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_SERIALIZATION_H_
 
 #include <type_traits>
 
 #include "mojo/public/cpp/bindings/lib/array_internal.h"
@@ skipping 50 matching lines @@
         typename WrapperTraits<S>::DataType>::type,
     true,
     false> {
   typedef
       typename std::remove_pointer<typename WrapperTraits<S>::DataType>::type
           S_Data;
   static size_t GetBaseArraySize(size_t count) {
     return count * sizeof(StructPointer<S_Data>);
   }
   static size_t GetItemSize(const S& item) {
-    return GetSerializedSize_(*UnwrapConstStructPtr<S>::value(item));
+    return !item.is_null()

[viettrungluu, 2015/12/07 22:03:51]

nit: Is S not testable? (I.e., would |return item ? ... : ...;| work instead?)

[vardhan, 2015/12/07 22:48:31]

Done.
It's testable.  I was trying to be more explicit about |item| not being a
pointer, but now realize that should be abstracted away.

+               ? GetSerializedSize_(*UnwrapConstStructPtr<S>::value(item))
+               : 0;
   }
 };
 
 template <typename U, typename U_Data>
 struct MapSerializer<U, U_Data, true, true> {
   static size_t GetBaseArraySize(size_t count) {
     return count * sizeof(U_Data);
   }
   static size_t GetItemSize(const U& item) {
     return GetSerializedSize_(item, true);
@@ skipping 121 matching lines @@
 
     *output = Map<MapKey, MapValue>(keys.Pass(), values.Pass());
   } else {
     output->reset();
   }
 }
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_SERIALIZATION_H_