Adjust idle notification handler to do full GC at the end of idle round in order to compact code space.

R=mstarzinger@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10639002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11900 ce2b1a6d-e550-0410-aec6-3dcde31c8c00