Collect cumulative (--print-cumulative-gc-stat) and per collection (--trace-gc-nvp) GC statistics and output it in a machine-readable name=value format.

Review URL: http://codereview.chromium.org/2132005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4675 ce2b1a6d-e550-0410-aec6-3dcde31c8c00