function getUserMedia(permission, constraints, successCallback, errorCallback) {
    navigator.mediaDevices
                .getUserMedia(constraints)
                .then(successCallback, reject)
                .catch(defaultRejectOrCatch);

    function reject(e) {
        if (errorCallback)
            errorCallback(e);
        else
            defaultRejectOrCatch(e);
    }
}

function defaultRejectOrCatch(e) {
    testFailed('getUserMedia failed:' + e);
    finishJSTest();
}

function setupVideoElementWithStream(stream)
{
    mediaStream = stream;
    testPassed('mediaDevices.getUserMedia generated a stream successfully.');
    evalAndLog('video.srcObject = mediaStream');
}