The current check is |NS_STYLE_DISPLAY_INLINE == mStyleDisplay->mOriginalDisplay|. Seems like it should be more like the check IsInlineOutside() does.
David, any objections?
Right now Presto has the same behavior we do for inline-block, at least, while WebKit and Trident (IE9) do something like IsInlineOutside().
*** This bug has been marked as a duplicate of bug 505706 ***