This is a temporary fix to prevent excessive expansion of old-space
caused by inaccuracies in lazy sweeper advancing. We actually don't
intend to sweep any pages eagerly, but that requires further changes
to lazy sweeping.

R=ulan@chromium.org,erik.corry@gmail.com
BUG=v8:2194

Review URL: https://chromiumcodereview.appspot.com/10640002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11904 ce2b1a6d-e550-0410-aec6-3dcde31c8c00