Test css coverage.

Initial coverage:
Coverage delta (8 entries)
    css/resources/coverage.css: +0-35 +36-56 +57-74 +105-135 +141-191 +327-517 +529-546 +596-634

Load stylesheet coverage2.css:
Coverage delta (1 entries)
    css/resources/coverage2.css: +95-151

Use class: "usedSomewhatLater"
Coverage delta (1 entries)
    css/resources/coverage2.css: +34-93

Use class: "usedAtTheVeryEnd"
Coverage delta (1 entries)
    css/resources/coverage2.css: +153-209