The following test is failing almost 100% of the time on Mojave release bots:

    TestWebKitAPI.WebKit2.SpeechRecognitionErrorWhenStartingAudioCaptureOnDifferentPage
        _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
        _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
        _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
        _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
        
        /Volumes/Data/slave/mojave-release/build/Tools/TestWebKitAPI/Tests/WebKitCocoa/SpeechRecognition.mm:194
        Expected equality of these values:
          @"Recorder Mute"
            Which is: "Recorder Mute"
          [lastScriptMessage body]
            Which is: "Recorder Error : ReferenceError: Can't find variable: MediaRecorder"

https://results.webkit.org/?suite=api-tests&test=TestWebKitAPI.WebKit2.SpeechRecognitionErrorWhenStartingAudioCaptureOnDifferentPage