The stack trace string is an ancient relic that is no longer being used.
We use the structured stack trace object instead.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/159013002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19264 ce2b1a6d-e550-0410-aec6-3dcde31c8c00