Ensure style invalidation bits reach the document root when inserting elements into the DOM.

Otherwise, situations may occur in which stale style invalidation bits are left
around when removing elements from the DOM while the bits are still present, and
re-inserting them. This is what happened in the attached bug.

BUG=350350

Review URL: https://codereview.chromium.org/197773002

git-svn-id: svn://svn.chromium.org/blink/trunk@169279 bbb929c8-8fbe-4397-9dbb-9b2b20218538