[Payments] secure-payment-confirmation should be the only method.

This cl throws a range error when extra payment methods are specified
along with "secure-payment-confirmation".

Change-Id: I68b321a123fb9df8d61f733f1c6e81f024e21d61
Bug: 1110320
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2340670Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797209}

third_party/blink/renderer/modules/payments/payment_request.cc

@@ -98,6 +98,7 @@ const char kAndroidPayMethod[] = "https://android.com/pay";
 const char kGooglePlayBillingMethod[] = "https://play.google.com/billing";
 const char kUnknownCurrency[] = "ZZZ";
 const char kAppStoreBillingLabelPlaceHolder[] = "AppStoreBillingPlaceHolder";
+const char kSecurePaymentConfirmationMethod[] = "secure-payment-confirmation";
 
 }  // namespace
 
@@ -438,7 +439,7 @@ void StringifyAndParseMethodSpecificData(ExecutionContext& execution_context,
   if (supported_method == "basic-card") {
     BasicCardHelper::ParseBasiccardData(input, output->supported_networks,
                                         exception_state);
-  } else if (supported_method == "secure-payment-confirmation" &&
+  } else if (supported_method == kSecurePaymentConfirmationMethod &&
              RuntimeEnabledFeatures::SecurePaymentConfirmationEnabled(
                  &execution_context)) {
     SecurePaymentConfirmationHelper::ParseSecurePaymentConfirmationData(
@@ -676,6 +677,18 @@ void ValidateAndConvertPaymentMethodData(
       return;
     }
 
+    if (payment_method_data->supportedMethod() ==
+            kSecurePaymentConfirmationMethod &&
+        input.size() > 1 &&
+        RuntimeEnabledFeatures::SecurePaymentConfirmationEnabled(
+            &execution_context)) {
+      exception_state.ThrowRangeError(
+          String(kSecurePaymentConfirmationMethod) +
+          " must be the only payment method identifier specified in the "
+          "PaymentRequest constructor.");
+      return;
+    }
+
     method_names.insert(payment_method_data->supportedMethod());
 
     output.push_back(payments::mojom::blink::PaymentMethodData::New());