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

components/payments/content/payment_request_web_contents_manager.h

 // 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.
 
 #ifndef COMPONENTS_PAYMENTS_PAYMENT_REQUEST_WEB_CONTENTS_MANAGER_H_
 #define COMPONENTS_PAYMENTS_PAYMENT_REQUEST_WEB_CONTENTS_MANAGER_H_
 
 #include <memory>
 #include <unordered_map>
 
@@ skipping 32 matching lines @@
   // Creates the PaymentRequest that will interact with this |web_contents|.
   void CreatePaymentRequest(
       content::WebContents* web_contents,
       std::unique_ptr<PaymentRequestDelegate> delegate,
       mojo::InterfaceRequest<payments::mojom::PaymentRequest> request,
       PaymentRequest::ObserverForTest* observer_for_testing);
 
   // Destroys the given |request|.
   void DestroyRequest(PaymentRequest* request);
 
+  // Called when |request| has received the show() call. Returns true if the
+  // |request| can be shown. (Only one request at a time can be shown per tab.)

[Mathieu, 2017/05/08 13:01:42]

you should add that this manager will now assume that |request| is showing (the
name CanShow is misleading because it has side effects. WillShow could be better
although I'm bad with names).

[please use gerrit instead, 2017/05/08 13:12:35]

Done.

+  bool CanShow(PaymentRequest* request);
+
  private:
   explicit PaymentRequestWebContentsManager(content::WebContents* web_contents);
   friend class content::WebContentsUserData<PaymentRequestWebContentsManager>;
   friend class PaymentRequestBrowserTestBase;
 
   // Owns all the PaymentRequest for this WebContents. Since the
   // PaymentRequestWebContentsManager's lifetime is tied to the WebContents,
   // these requests only get destroyed when the WebContents goes away, or when
   // the requests themselves call DestroyRequest().
   std::unordered_map<PaymentRequest*, std::unique_ptr<PaymentRequest>>

[Mathieu, 2017/05/08 13:01:42]

per Brett's email to chromium-dev, unordered_map is not efficient. Let's use
std::map

https://chromium.googlesource.com/chromium/src/+/master/base/containers/READM...

[please use gerrit instead, 2017/05/08 13:12:35]

Done.

       payment_requests_;
 
+  // The currently displayed instance of PaymentRequest. Points to one of the
+  // elements in payment_requests_. Can be null.
+  PaymentRequest* showing_;
+
   DISALLOW_COPY_AND_ASSIGN(PaymentRequestWebContentsManager);
 };
 
 }  // namespace payments
 
 #endif  // COMPONENTS_PAYMENTS_PAYMENT_REQUEST_WEB_CONTENTS_MANAGER_H_