PaymentApp: Implement nativeGetAllAppManifests

This change connects the ServiceWorkerPaymentAppBridge to the service
worker payment app code in content/browser/payments. This allows
installed service worker payment apps to show up in the Payment Request
dialog.

I also replace "String scopeUrl" with "long registrationId" as the
identifier for service worker payment apps.

This code is protected by the kServiceWorkerPaymentApps feature flag.

BUG=661608

Review-Url: https://codereview.chromium.org/2586213002
Cr-Commit-Position: refs/heads/master@{#440746}
8 files changed