Incorrect Static Position of Absolute Positioned Elements inside Rel-Positioned Containers

Per http://www.w3.org/TR/CSS2/visudet.html#abs-non-replaced-width if an
absolute positioned box's 'left' and 'right' values are both auto then it
should position itself as though it is a normal flow box in relation to its
containing block. Where the positioned box's container is a rel-positioned
inline we should disregard any offset created by that inline when
positioning the positioned box's layer.

This bug was spotted during a discussion at
http://lists.w3.org/Archives/Public/www-style/2014Jul/0549.html. The tests
are drawn from that discussion and attributed appropriately.

BUG=398164

Review URL: https://codereview.chromium.org/423173003

git-svn-id: svn://svn.chromium.org/blink/trunk@180488 bbb929c8-8fbe-4397-9dbb-9b2b20218538