Reset in-flight payment request & delay timer on new payment request

[slde12]

Previously, if consecutive payment requests invoke and close immediately before loading view finishes loading, the timer from previous payment request will try to openWindow after its timer times out.

This change fixes this by:

• Storing delay timer ID in global currentPayment.delayTimtoutId
• Canceling any pending timer via clearTimeout() and resetting global payment state when a new paymentrequest event arrives.
• Resetting delayTimeoutId to null upon normal timer completion.

[stephenmcgruer]

Is it feasible instead to update the service worker to handle multiple in-flight payment requests? Or is it too complicated to coordinate messages/etc in that scenario?

[stephenmcgruer]

Is it feasible instead to update the service worker to handle multiple in-flight payment requests? Or is it too complicated to coordinate messages/etc in that scenario?

Discussed offline, we will do this as a follow-up