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

components/payments/content/payment_request_web_contents_manager.cc

 // Copyright 2017 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_web_contents_manager.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 22 matching lines @@
     mojo::InterfaceRequest<payments::mojom::PaymentRequest> request,
     PaymentRequest::ObserverForTest* observer_for_testing) {
   auto new_request = base::MakeUnique<PaymentRequest>(
       web_contents, std::move(delegate), this, std::move(request),
       observer_for_testing);
   PaymentRequest* request_ptr = new_request.get();
   payment_requests_.insert(std::make_pair(request_ptr, std::move(new_request)));
 }
 
 void PaymentRequestWebContentsManager::DestroyRequest(PaymentRequest* request) {
+  if (request == showing_)
+    showing_ = nullptr;
   payment_requests_.erase(request);
 }
 
+bool PaymentRequestWebContentsManager::CanShow(PaymentRequest* request) {
+  DCHECK(request);
+  DCHECK(payment_requests_.find(request) != payment_requests_.end());
+  if (!showing_) {
+    showing_ = request;
+    return true;
+  } else {
+    return false;
+  }
+}
+
 PaymentRequestWebContentsManager::PaymentRequestWebContentsManager(
-    content::WebContents* web_contents) {}
+    content::WebContents* web_contents)
+    : showing_(nullptr) {}
 
 }  // namespace payments