如何保存firefox的本地流媒体视频

Question

我正在尝试分享屏幕。我实际上使用了html的视频标签来播放视频，然后我正在使用此视频的播放选项。现在我想将视频保存在我的电脑中。我将如何实现它。供参考，下面是代码：

var video = document.getElementById("video");

// Test browser support
window.navigator = window.navigator || {};
navigator.getUserMedia = navigator.getUserMedia ||
                         navigator.webkitGetUserMedia ||
                         navigator.mozGetUserMedia ||
                         null;

if (navigator.getUserMedia === null) {
    // document.getElementById('gum-unsupported').classList.remove('hidden');
    document.getElementById('videorecorderplay-button-recorder').setAttribute('disabled', 'disabled');
    document.getElementById('videorecorderstop-button-recorder').setAttribute('disabled', 'disabled');
} else {
    // Opera <= 12.16 accepts the direct stream.
    // More on this here: http://dev.opera.com/articles/view/playing-with-html5-video-and-getusermedia-support/
    var createSrc = window.URL ? window.URL.createObjectURL : function (stream) { return stream; };

    // Opera <= 12.16 support video only.
    var audioContext = window.AudioContext ||
                       window.webkitAudioContext ||
                       null;
    if (audioContext === null) {
        document.getElementById('gum-partially-supported').classList.remove('hidden');
    }

    //document.getElementById('videorecorderplay-button-recorder').addEventListener('click', function () {
    var constraints = {}
    constraints = {
        video: {
            mandatory: {
                minWidth: 1280,
                minHeight: 720,
                minFrameRate: 30
            },
            optional: [
              { minFrameRate: 60 }
            ],
            mediaSource: "screen"
        },        

    };
    // Capture user's audio and video source

    navigator.mozGetUserMedia(constraints, function(stream) {
        console.log("Received local stream");
        videoStream = stream;
        video.src = createSrc(stream);
        video.play();
    },
    function (error) {
        console.log("Video capture error: ", error.code);
    });        

}

一旦我调用video.play（），我的屏幕共享就开始了。现在我要保存它。我将如何做到这一点。