Mojo C++ bindings: better log message for serialization warnings.

mojo/public/cpp/bindings/lib/array_serialization.h

Index: mojo/public/cpp/bindings/lib/array_serialization.h
diff --git a/mojo/public/cpp/bindings/lib/array_serialization.h b/mojo/public/cpp/bindings/lib/array_serialization.h
index 492de788b4530f4997101b8772cd864958e1845b..cce60fdc829503c6c23830ebc5b3ccf9d03edbd8 100644
--- a/mojo/public/cpp/bindings/lib/array_serialization.h
+++ b/mojo/public/cpp/bindings/lib/array_serialization.h
@@ -104,7 +104,8 @@ template <typename H> struct ArraySerializer<ScopedHandleBase<H>, H, true> {
       MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(
           IsNonNullableValidationEnabled() && !element_is_nullable &&
               !output->at(i).is_valid(),
-          VALIDATION_ERROR_UNEXPECTED_INVALID_HANDLE);
+          VALIDATION_ERROR_UNEXPECTED_INVALID_HANDLE,
+          "invalid handle in array of non-nullable handles");
     }
   }
   static void DeserializeElements(
@@ -135,7 +136,8 @@ template <typename S> struct ArraySerializer<S, typename S::Data_*, true> {
       output->at(i) = element;
       MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(
           IsNonNullableValidationEnabled() && !element_is_nullable && !element,
-          VALIDATION_ERROR_UNEXPECTED_NULL_POINTER);
+          VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
+          "null pointer in array of non-nullable pointers");

[hansmuller, 2014/08/21 00:26:40]

You could specify the element index in the error message. It would help the
reader if it were possible to name the field or parameter that the array came
from, but that's going to be relatively difficult.

[yzshen1, 2014/08/21 05:57:49]

Done.

     }
   }
   static void DeserializeElements(
@@ -194,7 +196,8 @@ template <> struct ArraySerializer<String, String_Data*, false> {
       output->at(i) = element;
       MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(
           IsNonNullableValidationEnabled() && !element_is_nullable && !element,
-          VALIDATION_ERROR_UNEXPECTED_NULL_POINTER);
+          VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
+          "null string in array of non-nullable strings");
     }
   }
   static void DeserializeElements(
@@ -223,7 +226,8 @@ inline void SerializeArray_(Array<E> input, internal::Buffer* buf,
     MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(
         ValidateParams::expected_num_elements != 0 &&
             input.size() != ValidateParams::expected_num_elements,
-        internal::VALIDATION_ERROR_UNEXPECTED_ARRAY_HEADER);
+        internal::VALIDATION_ERROR_UNEXPECTED_ARRAY_HEADER,
+        "fixed-size array has wrong number of elements");
 
     internal::Array_Data<F>* result =
         internal::Array_Data<F>::New(input.size(), buf);