When we update the region range of a box we always relayout if the range has changed. This can be optimized in simple cases, when the box doesn't contain any trailing floats (that don't affect the height of the block).
Created attachment 231446 [details]
Comment on attachment 231446 [details]
Clearing flags on attachment: 231446
Committed r168836: <http://trac.webkit.org/changeset/168836>
All reviewed patches have been landed. Closing bug.