Implement missing TextLayout attributes

[cmyr]

There is a todo in code to add these missing attributes but I didn't see a tracking issue, so forgive me if I missed it somewhere; I would like to have an issue I can link to from a downstream project that will eventually want to use this API.

Thanks!

[alexcrichton]

Oh oops, thanks for the report! Should be fine to just uncomment those and we should be good to go!