This bug is not currently tracked.
Bug 1516089 removes the styles for .inset and .outset. We use the class inset at two places.
Bug 1516089 is on autoland.
The first occurrence is in prefs/Security/Junk "Show log". The border around the log in the dialog.
The second is in Account Settings/Outgoing Server (SMTP) the box below the "Details of selected server:".
Comment on attachment 9036418 [details] [diff] [review]
The change in dialog.css is a little different to what we had, but I'm sure you have your reasons. I didn't try it since I don't have time to rebuild now.
Pushed by email@example.com:
Restore CSS formerly provided by .inset after its removal in bug 1516089. r=jorgk
Yes, the border colour was defined in the removed hunk in aboutPreferences.css. I changed to the variable instead of hard coding it. Also the margin fits better to the margins we use in in-content pages.