Revert "compareDocumentPosition() should report PRECEEDING or FOLLOWING information even if nodes are disconnected"

This reverts r154835 due to flaky layout test failures.
These failures are almost certainly due to tying the result of
compareDocumentPosition to pointer comparisons (e.g., "this > otherNode").

TBR=ch.dumez@sisa.samsung.com
BUG=263340

Review URL: https://codereview.chromium.org/20162003

git-svn-id: svn://svn.chromium.org/blink/trunk@154853 bbb929c8-8fbe-4397-9dbb-9b2b20218538