Make sure a test that fails two different ways is considered a failure

and not a flaky test (although technically it is both).

R=ojan@chromium.org
BUG=307277

Review URL: https://codereview.chromium.org/27232004

git-svn-id: svn://svn.chromium.org/blink/trunk@159630 bbb929c8-8fbe-4397-9dbb-9b2b20218538