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

mojo/public/cpp/bindings/lib/validation_errors.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_VALIDATION_ERRORS_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_VALIDATION_ERRORS_H_
 
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
@@ skipping 82 matching lines @@
 
 // In debug build, logs a serialization warning if |condition| evaluates to
 // true:
 //   - if there is a SerializationWarningObserverForTesting object alive,
 //     records |error| in it;
 //   - otherwise, logs a fatal-level message.
 // |error| is the validation error that will be triggered by the receiver
 // of the serialzation result.
 //
 // In non-debug build, does nothing (not even compiling |condition|).
-#define MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(condition, error) \
-    MOJO_DLOG_IF(FATAL, (condition) && !ReportSerializationWarning(error)) \
-        << "The outgoing message will trigger " \
-        << ValidationErrorToString(error) << " at the receiving side.";
+#define MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING( \
+    condition, error, description) \
+  MOJO_DLOG_IF(FATAL, (condition) && !ReportSerializationWarning(error)) \
+      << "The outgoing message will trigger " \
+      << ValidationErrorToString(error) << " at the receiving side (" \
+      << description << ").";
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_VALIDATION_ERRORS_H_