For SubDialogs in the TabDialogBox, when resizing the main browser window to be smaller in width than the SubDialog, the content can wrap into the next line causing to clip.
Bug 1141031 fixed this for SubDialogs which live in content (about:preferences) by setting a min-width. However, this doesn't work for SubDialogs in the parent (in the TabDialogBox). When a min-width is set it prevents the parent chrome from properly collapsing.
We should resize the SubDialog vertically when the content wraps.