Following on from T15667,

• Update ArcanistXUnitTestResultParser->parseTestResults() to take a second argument, $path, which, if provided and $test_results is empty, will mimic the ArcanistPhpunitTestResultParser->parseTestResults() behaviour in returning a RESULT_BROKEN ArcanistUnitTestResult. I find this preferable to throwing an exception.
• Move the ArcanistPhpunitTestResultParser->readCoverage() into a new ArcanistCloverCoverageParser.php