[CSSOM] offsetWidth, offsetLeft issues

The following rules are always true in IE

bounding box of getClientRects is always the same as getBoundingClientRect
The width and height of getBoundingClientRect is always the same as
offsetWidth and offsetHeight.

However, http://www.w3.org/TR/cssom-view/#offset-attributes says it
should return the border edge. In most cases this is the same but once
again tables with captions roars its ugly head. The border edge of a
table with a caption does not include the caption and therefore the
rules above do not hold true.

Like, with getClientRects only Firefox follows the spec.

-- 
erik