This allows one to spot fragmentation issues just by looking at --trace-gc output.

R=erik.corry@gmail.com

Review URL: https://chromiumcodereview.appspot.com/9316060

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10584 ce2b1a6d-e550-0410-aec6-3dcde31c8c00