While selecting in a subframe, we have to check that the selection reaches the bottom of the current subframe instead of the page.
Created attachment 192925 [details] Patch
Comment on attachment 192925 [details] Patch LGTM.
Comment on attachment 192925 [details] Patch Clearing flags on attachment: 192925 Committed r145720: <http://trac.webkit.org/changeset/145720>
All reviewed patches have been landed. Closing bug.