clientHeight should include padding but exclude scrollbars (and RenderBox::clientHeight does!). RenderBox::computeLogicalClientHeight returns the box-sizing adjusted content height (excluding both padding and scrollbars). It's especially confusing because computeContentLogicalHeightUsing returns the content height not adjusted for box-sizing and including the scrollbar and computeLogicalHeightUsing returns the border-box size (including scrollbar obviously).
Can't think of a better name at the moment, but computeLogicalClientHeight is definitely wrong.
Created attachment 163700 [details]
Comment on attachment 163700 [details]
Clearing flags on attachment: 163700
Committed r128371: <http://trac.webkit.org/changeset/128371>
All reviewed patches have been landed. Closing bug.