browser.permissions.request doesn't return a promise

[olsh]

Browser: Chrome 58
Library version: 0.1.1

I'm using this code on an extension options page:

browser.permissions.request({
            origins: ["<all_urls>"]
        }).then(function (granted) {
                // do something
            })

The popup request is showing, but the code throws the error:

Uncaught TypeError: Cannot read property 'then' of undefined

[shatgupt]

Encountered this issue while trying to use optional permissions.

[romantaraban]

The library is missing definitions for permissions API in api-metadata.json, please see #44

[sladiri]

Could you please explain how this issue is resolved? I cannot get my version of this permissions example to work, since browser.permissions.request({ permissions: ['history'] }) never resolves. If I try to grant this permission in my extension, it also breaks the original exmple extension (the permission popup never appears).
Firefox 67.0b16 (64-bit)

https://github.com/mdn/webextensions-examples/blob/master/permissions/page.js

I created a repo with my code:
https://github.com/sladiri/web-extension-test/blob/master/src/permissions.js#L13

[sladiri]

I was unaware that this API is new and seems to be not really consistent yet. So I guess I just have to wait, I have the same experience as in this answer on SO https://stackoverflow.com/a/47729896/7309920
I understand that such an API requires careful design so that it cannot be abused.