How to save a local streaming video of firefox - html

Question

I am trying to share screen. I have actually used the video tag of html to stream video and then I am using the play option of this video. Now I want to save the video in my computer. How will I achieve it. For reference, below is the code:
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);
});
}
Once I am calling the video.play(), my screen sharing start. Now I want to save it. How will I do this.