Bug 1080832 - [Messages][RTL] Cursor is badly located in recipients and subject when they are empty. r=julien

From an accessibility perspective, that empty space that a user clicks needs to have an appropriate role. I had the entry grow and take up all that space, so that a blind user will have an easier time finding it. In other words, the recipient list looks like this in accessibility:
[recipient button], [recipient button], [entry        ]