This patch basically does:
* Add descriptor setters and generation count to CounterStyleRule in
Servo. (This code is mostly based on the old code inside
nsCSSCounterStyleRule for handling mutation.)
* Use RawServoCounterStyleRule in CounterStyleManager.
* Add ServoCounterStyleRule and remove nsCSSCounterStyleRule.
Test change:
* "fixed" was parsed as and thus serialized to "fixed 1", but Servo
doesn't do so. It preserves whether the number presents. Either way
is probably fine.
MozReview-Commit-ID: EtKTeu32isi