Bug 1105857 - [Messages] User doesn't receive any notification about incoming message if native modal dialog is shown. r=schung

could you please replace this:
`
form[role="dialog"][data-type="confirm"] menu button:last-child {
margin-left: 1rem;
}
form[role="dialog"][data-type="confirm"] menu button,
form[role="dialog"][data-type="confirm"] menu button:first-child {
margin: 0 0.5rem;
}
`
width:
`
form[role="dialog"][data-type="confirm"] menu button {
  margin: 0 1rem 0 0;
}

form[role="dialog"][data-type="confirm"] menu button:last-child {
  margin-right: 0;
}
`
This way we could use 3 buttons, even is not recommended :)