[Payments] Have an observer for canMakePayment, for testing.

chrome/browser/payments/payment_request_factory.cc

Index: chrome/browser/payments/payment_request_factory.cc
diff --git a/chrome/browser/payments/payment_request_factory.cc b/chrome/browser/payments/payment_request_factory.cc
index fc6c4ca29937261b5057190143be4503f75460e5..8f532f9c49b49aeb709b128d73d5934affd40d88 100644
--- a/chrome/browser/payments/payment_request_factory.cc
+++ b/chrome/browser/payments/payment_request_factory.cc
@@ -20,10 +20,11 @@ void CreatePaymentRequestForWebContents(
     mojo::InterfaceRequest<payments::mojom::PaymentRequest> request) {
   DCHECK(web_contents);
   PaymentRequestWebContentsManager::GetOrCreateForWebContents(web_contents)
-      ->CreatePaymentRequest(web_contents,
-                             base::MakeUnique<ChromePaymentRequestDelegate>(
-                                web_contents),
-                             std::move(request));
+      ->CreatePaymentRequest(
+          web_contents,
+          base::MakeUnique<ChromePaymentRequestDelegate>(web_contents),
+          std::move(request),
+          /*observer_for_testing=*/nullptr);
 }
 
 }  // namespace payments