Now that this is a pref that is different in different versions, tests
have to work no matter what the pref's value is. For tests that
actually tested line-breaking-related behavior, I made them test all
three separator values. For tests that tested something else and only
incidentally depend on the default paragraph separator, I set
defaultParagraphSeparator to "div".
MozReview-Commit-ID: 8m7eoFRXpEy
c71f7a4cf7