Facebook JS connect unsupported browser
It's been around since Chrome 19.
Check here https://developers.facebook.com/bugs/325086340912814/ for more details.
I'm not sure if there will be a workaround or fix soon.This issue was logged about 10 months ago.
I've been struggling with this for awhile.
This may not be a perfect solution but I was able to get around this by getting the login url using the PHP SDK (https://developers.facebook.com/docs/reference/php/facebook-getLoginUrl/) and linking that to the Facebook button. It works on Chrome mobile.
I'm not sure if there's an equivalent to the getLoginUrl for the JS SDK.