[TESTS] add Global Styles / Create Test for constructed sytlesheets

Tests should cover:

- ORDER of adopted styles in shadow DOM must be the same as in light DOM
- url() functions in css are resolved relative to the css file in any browser. (was broken (or correct :D) in safari)

The url issue led to broken (to font files relative to the location path) requests created by elements that were adopting the css with the font-family.



