By making Run's last entry to expand as we add fragments. -instead of having LineState:segment (and related) members.
Created attachment 245749 [details] Patch
Created attachment 245751 [details] Patch
Comment on attachment 245751 [details] Patch r=me
Comment on attachment 245751 [details] Patch Clearing flags on attachment: 245751 Committed r179435: <http://trac.webkit.org/changeset/179435>
All reviewed patches have been landed. Closing bug.