UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.0.1 Safari/605.1.15

Steps to reproduce the problem:
The payment request API int

1. Run WPT payment-request/billing-address-changed-manual.https.html

3. 

What is the expected behavior?
The ability to request a billing address. 

What went wrong?
The `requestBillingAddress` and `PaymentMethodChannge` event are not currently supported. 

Did this work before? No 

Does this work in other browsers? No
 Gecko: 
https://bugzilla.mozilla.org/show_bug.cgi?id=1477117

Chrome version: <Copy from: 'about:version'>  Channel: n/a
OS Version: OS X 10.14.1
Flash Version: 

This is Payment Request pull request https://github.com/w3c/payment-request/pull/749