If selection reaches the bottom of content, just ignore scroll margin so the text on the bottom can be selected.
Created attachment 194344 [details] Patch
Comment on attachment 194344 [details] Patch LGTM.
Comment on attachment 194344 [details] Patch Clearing flags on attachment: 194344 Committed r146528: <http://trac.webkit.org/changeset/146528>
All reviewed patches have been landed. Closing bug.