Passes in predictable mode were wrongly reported as failures by the json progress indicator. This moves control about what is reported completely to execution.py.

BUG=391747
LOG=n
R=ishell@chromium.org, jkummerow@chromium.org

Review URL: https://codereview.chromium.org/382443004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22299 ce2b1a6d-e550-0410-aec6-3dcde31c8c00