[css] accumulate the score from parent and ancestor matches
[css] accumulate the score from parent and ancestor matches

The score from matching parents and ancestors should be included in
the final score, since more specific selectors should get a greater
score.

pwithnall/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx