chrome-polyfill.js

(function(){
    if(navigator.userAgent.toLowerCase().indexOf('chrome') > -1){
 
        // Work around https://bugs.chromium.org/p/chromium/issues/detail?id=622956
        // Chrome does not fire the empty keystatuschange event when a session is closed
        var _mediaKeySessionClose = MediaKeySession.prototype.close;
        var _mediaKeySessionKeyStatusesGetter = Object.getOwnPropertyDescriptor( MediaKeySession.prototype, 'keyStatuses' ).get;
        var _emptyMediaKeyStatusMap = { size: 0,
                                        has:    function() { return false; },
                                        get:    function() { return undefined; },
                                        entries:function() { return []; },          // this may not be correct, I think it should be some iterator thing
                                        keys:   function() { return []; },
                                        values: function() { return []; },
                                        forEach:function() { return; } };
 
        MediaKeySession.prototype.close = function close()
        {
            this.__closed = true;
 
            setTimeout( function() { this.dispatchEvent( new Event( 'keystatuseschange' ) ); }.bind( this ), 0 );
 
            return _mediaKeySessionClose.call( this );
        };
 
        Object.defineProperty( MediaKeySession.prototype, 'keyStatuses', { get: function() {
        
            return this.__closed ? _emptyMediaKeyStatusMap : _mediaKeySessionKeyStatusesGetter.call( this );
        
        } } );
    }
}());