Propagate purple step status to top-level build status
Propagate purple step status to top-level build status

See https://groups.google.com/a/chromium.org/d/msg/infra-dev/zTL15fwspt0/ADjDGFOdu9sJ
for context.

BUG=377805

Review URL: https://codereview.chromium.org/494143002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@291635 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build