[selectors-4] Import W3C Test Suite

This patch imports "selectors-4" test suite from W3C csswg-test repo:
https://github.com/w3c/csswg-test/tree/master/selectors-4/

Only 2 tests are passing right now. Other fail because of
the psuedo-classes haven't been implemented yet:
:dir (crbug.com/576815) and :focus-within (crbug.com/617371).

BUG=704902

Review-Url: https://codereview.chromium.org/2776693002
Cr-Commit-Position: refs/heads/master@{#459401}
32 files changed