Make DM failures fatal

We should now only be pushing Srcs for tests that we expect
to succeed.  So any failures should be treated as errors.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1719293002

Review URL: https://codereview.chromium.org/1719293002
2 files changed