Remove more stuff from applyAuthorStyles.

There's a lot of machinery that's realted to <style scoped> and
applyAuthorStyles that's now dead and is just making things slower. Lets
remove it all.

BUG=372083

Review URL: https://codereview.chromium.org/581663003

git-svn-id: svn://svn.chromium.org/blink/trunk@182291 bbb929c8-8fbe-4397-9dbb-9b2b20218538