New flakiness dashboard shouldn't treat tests with right expectations as failing

New flakiness dashboard shouldn't treat tests with right expectations as failing
https://bugs.webkit.org/show_bug.cgi?id=123385

Reviewed by Alexey Proskuryakov.

We define failing tests to be tests with wrong expectations whose actual results are not PASS
since tests with TEXT, IMAGE, etc... failures do not turn the bots red as long as the expectation
of the same type is specified in TestExpectation files.

* public/include/test-results.php:
(FailingResultsJSONWriter): Inherit from WrongExpectationsResultsJSONWriter.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@158093 268f45cc-cd09-0410-ab3c-d52691b4dbfc