When enabled, this dynamically adds jobs that had failures back to the pool. Special json output for flakes will be handled in a separate CL.

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

Review URL: https://codereview.chromium.org/360113003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22143 ce2b1a6d-e550-0410-aec6-3dcde31c8c00