The TableRow currently has some margin on the left, but not on the
right. This is visually unbalanced, especially when expanded so depth>0,
as the content on the right is at the very edge of the shaded rectangle.
This commit cleans that up a bit!
Test plan: Visual inspection (see screenshots in the pull request). I
don't think unit tests are necessary for small visual tweaks like this.
be79e3cb1c