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

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

Index: mojo/public/cpp/bindings/lib/array_internal.h
diff --git a/mojo/public/cpp/bindings/lib/array_internal.h b/mojo/public/cpp/bindings/lib/array_internal.h
index a047db26e0bb87a9018018d5a6ef0ce5ba74da0f..6b0baa0f07ce8e27fc5ebe2a5278bfd48fb7a971 100644
--- a/mojo/public/cpp/bindings/lib/array_internal.h
+++ b/mojo/public/cpp/bindings/lib/array_internal.h
@@ -27,6 +27,14 @@ namespace internal {
 // C++11).
 const uint32_t kMaxUint32 = 0xFFFFFFFF;
 
+std::string MakeMessageWithArrayIndex(const char* message,
+                                      size_t size,
+                                      size_t index);
+
+std::string MakeMessageWithExpectedArraySize(const char* message,
+                                             size_t size,
+                                             size_t expected_size);
+
 template <typename T>
 struct ArrayDataTraits {
   typedef T StorageType;