[Payments] Allow cancel payment request when loading instruments

chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java

Index: chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java b/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
index bbf43d898fa1cef4e3307d71a392e2ae874d5ba4..975e32bd6fc459db00ff1d9ede0302920b14e14a 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
@@ -1054,6 +1054,8 @@ public class PaymentRequestImpl
     public void onInstrumentDetailsLoadingWithoutUI() {
         if (mClient == null || mUI == null || mPaymentResponseHelper == null) return;
 
+        assert mPaymentMethodsSection.getSelectedItem() instanceof AutofillPaymentInstrument;
+
         mUI.showProcessingMessage();
         mPaymentResponseHelper.onInstrumentsDetailsLoading();
     }