How to track permission change for getUserMedia()?

Question

JavaScript

navigator.getUserMedia (
// constraints
{
video: true,
audio: true
},
// successCallback
function(localMediaStream) {
var video = document.querySelector('video');
video.src = window.URL.createObjectURL(localMediaStream);
video.onloadedmetadata = function(e) {
// Do something with the video here.
};
},
// errorCallback
function(err) {
if(err === PERMISSION_DENIED) {
// Explain why you need permission and how to update the permission setting
}
}
);

The problem is that the user, having allowed the use of the camera at the beginning, can deny access during recording by clicking on the icon in the address bar:

Tell me how to track the subsequent change in write access?