Fix markAncestorsWithChildNeedsStyleInvalidation to actually mark only ancestors.

Make corresponding fix to StyleInvalidator to not break invalidations in
which the document element itself needed invalidation.

Review URL: https://codereview.chromium.org/201443011

git-svn-id: svn://svn.chromium.org/blink/trunk@169788 bbb929c8-8fbe-4397-9dbb-9b2b20218538