Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The message event of the MediaKeySession interface fires when a message is generated by the content decryption module.
Use the event name in methods like addEventListener(), or set an event handler property.
addEventListener("message", (event) => { })
onmessage = (event) => { }A MediaKeyMessageEvent. Inherits from Event.