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..1c000ec33ed3be157d6b0a498eb3cf24856a95b8 100644
--- a/components/payments/content/payment_request_web_contents_manager.h
+++ b/components/payments/content/payment_request_web_contents_manager.h
@@ -5,8 +5,8 @@
 #ifndef COMPONENTS_PAYMENTS_PAYMENT_REQUEST_WEB_CONTENTS_MANAGER_H_
 #define COMPONENTS_PAYMENTS_PAYMENT_REQUEST_WEB_CONTENTS_MANAGER_H_
 
+#include <map>
 #include <memory>
-#include <unordered_map>
 
 #include "base/macros.h"
 #include "components/payments/content/payment_request.h"
@@ -50,6 +50,12 @@ class PaymentRequestWebContentsManager
   // Destroys the given |request|.
   void DestroyRequest(PaymentRequest* request);
 
+  // Called when |request| has received the show() call. If the |request| can be
+  // shown, then returns true and assumes that |request| is now showing until
+  // DestroyRequest(|request|) is called with the same pointer. (Only one
+  // request at a time can be shown per tab.)
+  bool CanShow(PaymentRequest* request);
+
  private:
   explicit PaymentRequestWebContentsManager(content::WebContents* web_contents);
   friend class content::WebContentsUserData<PaymentRequestWebContentsManager>;
@@ -59,8 +65,11 @@ class PaymentRequestWebContentsManager
   // 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>>
-      payment_requests_;
+  std::map<PaymentRequest*, std::unique_ptr<PaymentRequest>> 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);
 };