Comment 3 for bug 1735442

The commit 5e15470d8b3619772857c4205644c0677ef30a92 made the border in custom theme go from light grey to transparent.

This was fine when header background colour was dark as the button stood out from white page.

But with very light header background value the button disappears into the background.

Have made the button's border colour be the same as the header text colour