Add information about rerun tests to json output.

BUG=374134
LOG=n
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/364793004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22147 ce2b1a6d-e550-0410-aec6-3dcde31c8c00