Add "FAIL" to the set of possible results.

The gtest results are migrating to the run-webkit-tests aka
full_results format. Part of that change means there'll be a
"FAIL" result, which TestResultServer needs to understand.

This change is a prerequisite for the above change, https://chromiumcodereview.appspot.com/20492002/. 

BUG=247192

Review URL: https://chromiumcodereview.appspot.com/21090003

git-svn-id: svn://svn.chromium.org/blink/trunk@155353 bbb929c8-8fbe-4397-9dbb-9b2b20218538