Increase slots buffer chain length to 15 to make compaction more aggressive and usefull.

Pass gc and collector selection reasons to GCTracer to allow more meaningull --gc-trace.

Print fragmentation of spaces that we do not compact.

R=erik.corry@gmail.com

Review URL: https://chromiumcodereview.appspot.com/9323007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10601 ce2b1a6d-e550-0410-aec6-3dcde31c8c00