Also changed time reporting to system time to be able to get synchronized with other memory (e.g. DOM) size status.

Review URL: http://codereview.chromium.org/155764

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2509 ce2b1a6d-e550-0410-aec6-3dcde31c8c00