Verify behavior of PaymentRequest.show() method, part 1.

components/payments/content/payment_request.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/payments/content/payment_request.h"
 
 #include <string>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 81 matching lines @@
       delegate_->GetPersonalDataManager(), delegate_.get());
 }
 
 void PaymentRequest::Show() {
   if (!client_.is_bound() || !binding_.is_bound()) {
     LOG(ERROR) << "Attempted Show(), but binding(s) missing.";
     OnConnectionTerminated();
     return;
   }
 
+  // A tab can display only one PaymentRequest UI at a time.
+  if (!manager_->CanShow(this)) {
+    LOG(ERROR) << "A PaymentRequest UI is already showing";
+    client_->OnError(mojom::PaymentErrorReason::USER_CANCEL);
+    OnConnectionTerminated();
+    return;
+  }
+
   if (!state_->AreRequestedMethodsSupported()) {
     client_->OnError(mojom::PaymentErrorReason::NOT_SUPPORTED);
     if (observer_for_testing_)
       observer_for_testing_->OnNotSupportedError();
     OnConnectionTerminated();
     return;
   }
 
   journey_logger_.SetShowCalled();
   delegate_->ShowDialog(this);
@@ skipping 91 matching lines @@
   binding_.Close();
   delegate_->CloseDialog();
   manager_->DestroyRequest(this);
 }
 
 void PaymentRequest::Pay() {
   state_->GeneratePaymentResponse();
 }
 
 }  // namespace payments