Best I could do for now is to install the entire infobox tag folder, so you would have to pick the 1.1.9/ folder inside there.
"infobox": "svn+http://google-maps-utility-library-v3.googlecode.com/svn#infobox"
I'm almost sure that Bower does not support nested tag folders like these, as the entire project is based on Git that has a more strict logic for tags.
Hope this helps,