Allow multiple host pseudos in same compound.

As part of optimizing away :host(-context) selectors which never may
match, we also skipped selectors with multiple :host(-context) pseudos
in the same compound.

Removed assert in findBestRuleSetAndAdd as that would now be required
to traverse the whole compound again to cover everything.

BUG=601585

Review URL: https://codereview.chromium.org/1872343002

Cr-Commit-Position: refs/heads/master@{#387263}
4 files changed