[mojo] Add Mojo bindings support for IPC::ParamTraits

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

Index: mojo/public/cpp/bindings/lib/bindings_internal.h
diff --git a/mojo/public/cpp/bindings/lib/bindings_internal.h b/mojo/public/cpp/bindings/lib/bindings_internal.h
index 4c5917a1c61710b5640ad6b32e7024d825ed10fb..2ae181df1edaabe4ee060f51f611dee3cdbc1cbe 100644
--- a/mojo/public/cpp/bindings/lib/bindings_internal.h
+++ b/mojo/public/cpp/bindings/lib/bindings_internal.h
@@ -38,6 +38,14 @@ union StructPointer {
 static_assert(sizeof(StructPointer<char>) == 8, "Bad_sizeof(StructPointer)");
 
 template <typename T>
+union NativePointer {
+  uint64_t offset;
+  Array_Data<uint8_t>* ptr;
+};
+static_assert(sizeof(NativePointer<char>) == sizeof(StructPointer<char>),
+    "Bad_sizeof(NativePointer)");
+
+template <typename T>
 union ArrayPointer {
   uint64_t offset;
   Array_Data<T>* ptr;