Unlink evacuation candidates from list of pages before starting sweeper threads.
Removed FinalizeSweeping().

BUG=

Review URL: https://codereview.chromium.org/12499004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13886 ce2b1a6d-e550-0410-aec6-3dcde31c8c00