Disable some edge-case test with legal font family names because they fail in Internet Explorer.
Disable tests that rely on font-variant for Firefox. Also normalize property values.
Remove parentStyleSheet on CSSFontFaceRule because it is unused (except internally).
Remove ability to set cssText on CSSFontFaceRule. It is not used and broken on several browsers.
Disable CSSFontFaceRule.prototype.update test for IE9. Browsers that use it are testing the method through other code paths, so coverage should be the same.