[glom] Added a comment.

[Murray Cumming <murrayc src gnome org>]

commit eccf1c9d53373dee871324bf7bc9d0328018a525
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Feb 10 16:00:47 2016 +0100

    Added a comment.

 glom/libglom/data_structure/field.cc |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/glom/libglom/data_structure/field.cc b/glom/libglom/data_structure/field.cc
index 1c9894c..4e9a96c 100644
--- a/glom/libglom/data_structure/field.cc
+++ b/glom/libglom/data_structure/field.cc
@@ -783,6 +783,7 @@ Glib::ustring Field::get_type_name_ui(glom_field_type glom_type)
   return result;
 }
 
+//TODO: Performance, though this is a small map.
 //static:
 Field::glom_field_type Field::get_type_for_ui_name(const Glib::ustring& glom_type)
 {