Set the state of a swept page after being done with sweeping.

BUG=
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/408843003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22514 ce2b1a6d-e550-0410-aec6-3dcde31c8c00