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

components/payments/content/payment_request_web_contents_manager.h

Index: components/payments/content/payment_request_web_contents_manager.h
diff --git a/components/payments/content/payment_request_web_contents_manager.h b/components/payments/content/payment_request_web_contents_manager.h
index be08a3da0035226eb91044d9d85b61fd37c81ff8..6918520a9bf41ca10be847b02d0551cb2a90ed02 100644
--- a/components/payments/content/payment_request_web_contents_manager.h
+++ b/components/payments/content/payment_request_web_contents_manager.h
@@ -50,6 +50,10 @@ class PaymentRequestWebContentsManager
   // 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>;
@@ -62,6 +66,10 @@ class PaymentRequestWebContentsManager
   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);
 };