Parameterize OnError method.

third_party/WebKit/public/platform/modules/payments/payment_request.mojom

Index: third_party/WebKit/public/platform/modules/payments/payment_request.mojom
diff --git a/third_party/WebKit/public/platform/modules/payments/payment_request.mojom b/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
index 6a113f58e5ae63da1b2465db1ed0ffd6fb6ca470..28f741eaabe0600adc193abead86a678c192eba4 100644
--- a/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
+++ b/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
@@ -63,11 +63,17 @@ struct PaymentResponse {
   string? payer_phone;
 };
 
+enum PaymentErrorReason {
+  UNKNOWN,
+  USER_CANCEL,
+  NOT_SUPPORTED
+};
+
 interface PaymentRequestClient {
   OnShippingAddressChange(PaymentAddress address);
   OnShippingOptionChange(string shipping_option_id);
   OnPaymentResponse(PaymentResponse response);
-  OnError();
+  OnError(PaymentErrorReason error);
   OnComplete();
   OnAbort(bool aborted_successfully);
 };