[shadow-dom-tests] Adjusted queryselector to operate on the SR (#593)

I assume that querying from document into a Shadow Root isn't expected
to work. Made the query to operate on the SR which fixes the failing
test(s).

View on GitHub: https://github.com/w3c/web-platform-tests/pull/593

Received on Monday, 3 February 2014 09:00:01 UTC