Changes the Payment Handler API, to let the browser delegate handling of shipping address and payer's contact information to Payment Handlers.
Delegating shipping address and contact info data collection to payment handlers can lead to better user experience since the payment app may have more accurate information than the browser. Currently if shipping or contact information is required the browser always shows the payment sheet to collect the required information. With this delegation the browser can skip the payment sheet and show the payment handler window directly when the payment handler can handle shipping address/contact info. Skipping the payment sheet reduces checkout time since one step is skipped during the checkout. Additionally new user on boarding flow would have less friction since shipping/contact and payment information collection won't be split between the browser and the payment provider
Docs: https://docs.google.com/document/d/1rKwyBAvtOyGetlr55FQ3XqpFc6aGKG0qCQyuOaEbc00/edit?usp=sharing
Explainers: https://github.com/sahel-sh/shipping-contact-delegation/blob/master/Explainer.md