iframes with allowpaymentrequest attribute are allowed to make payment requests.

third_party/WebKit/Source/core/html/HTMLIFrameElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2004, 2006, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 10 matching lines @@
  *
  */
 
 #ifndef HTMLIFrameElement_h
 #define HTMLIFrameElement_h
 
 #include "core/CoreExport.h"
 #include "core/html/HTMLFrameElementBase.h"
 #include "core/html/HTMLIFrameElementPermissions.h"
 #include "core/html/HTMLIFrameElementSandbox.h"
+#include "platform/Supplementable.h"
 #include "public/platform/WebVector.h"
 #include "public/platform/modules/permissions/WebPermissionType.h"
 
 namespace blink {
 
-class CORE_EXPORT HTMLIFrameElement final : public HTMLFrameElementBase {
+class CORE_EXPORT HTMLIFrameElement final
+    : public HTMLFrameElementBase,
+      public Supplementable<HTMLIFrameElement> {
   DEFINE_WRAPPERTYPEINFO();
+  USING_GARBAGE_COLLECTED_MIXIN(HTMLIFrameElement);
 
  public:
   DECLARE_NODE_FACTORY(HTMLIFrameElement);
   DECLARE_VIRTUAL_TRACE();
   ~HTMLIFrameElement() override;
   DOMTokenList* sandbox() const;
   DOMTokenList* permissions() const;
 
   void sandboxValueWasSet();
   void permissionsValueWasSet();
@@ skipping 20 matching lines @@
   }
   void didLoadNonEmptyDocument() override { m_didLoadNonEmptyDocument = true; }
   bool isInteractiveContent() const override;
 
   ReferrerPolicy referrerPolicyAttribute() override;
 
   bool allowFullscreen() const override { return m_allowFullscreen; }
 
   AtomicString csp() const override { return m_csp; }
 
+  bool allowPaymentRequest() const override { return m_allowPaymentRequest; }

[please use gerrit instead, 2016/10/18 14:04:49]

I was under impression that this getter would live in
HTMLIFrameElementPayments.h when you specify
ImplementedAs=HTMLIframeElementPayments in HTMLIFrameElementPayments.idl. If
that's not possible for some reason or is the wrong thing to do, please let me
know. I'm also learning this area of the code for the first time.

[pals, 2016/10/19 05:09:53]

I am trying to move "m_allowPaymentRequest" to HTMLIFrameElementPayments.h but
not able to get allowpaymentrequestAttr in HTMLIFrameElementPayments.cpp. I am
not able find existing code where idl filename and ImplementedAs are having same
name. @haraken, could please suggest how this can be achived. 

[haraken, 2016/10/19 09:04:08]

Nice catch! rouslan is right. We should put m_allowPaymentRequest in
HTMLIFrameElementPayments.h.

Why do you need [ImplementedAs] in the first place? What happens if you simply
put m_allowPaymentRequest in HTMLIFrameElementPayments.h without using
[ImplementedAs]?

+
   const WebVector<WebPermissionType>& delegatedPermissions() const override {
     return m_delegatedPermissions;
   }
 
   bool initializePermissionsAttribute();
 
   AtomicString m_name;
   AtomicString m_csp;
   bool m_didLoadNonEmptyDocument;
   bool m_allowFullscreen;
+  bool m_allowPaymentRequest;

[please use gerrit instead, 2016/10/18 14:04:49]

Ditto

   Member<HTMLIFrameElementSandbox> m_sandbox;
   Member<HTMLIFrameElementPermissions> m_permissions;
 
   WebVector<WebPermissionType> m_delegatedPermissions;
 
   ReferrerPolicy m_referrerPolicy;
 };
 
 }  // namespace blink
 
 #endif  // HTMLIFrameElement_h