implement basic horizontal flexing
Created attachment 101762 [details] Patch
Lots of functionality is missing, but this implements basic horizontal flexing. I wanted to make sure this is on the right track.
Comment on attachment 101762 [details] Patch Looks ok. Lots of FIXMEs ,but what's there seems fine.
Committed r92628: <http://trac.webkit.org/changeset/92628>