Fix the loop-builder to tag the entire body as part of the loop.

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/21813004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16041 ce2b1a6d-e550-0410-aec6-3dcde31c8c00