I'm facing an unexpected behavior and wanted to be sure i'm not missing something before i'm filling a bug.

I've played with requestFullscreen on chrome and firefox and noticed it's not returning a promise like stated in the spec.

Example for webkit:

el.addEventListener('click', () => {

    const p = el.webkitRequestFullScreen();

    p.then(() => {console.log('full screen')});

});

I'm getting:

Uncaught TypeError: Cannot read property 'then' of undefined
at HTMLDivElement.el.addEventListener

Same goes for firefox:

el.addEventListener('click', () => {

    const p = el.mozRequestFullScreen();

    p.then(() => {console.log('full screen')});

});

TypeError: p is undefined

Am i reading the spec wrong? shouldn't i expect that promise?