iframes with allowpaymentrequest attribute are allowed to make payment requests.

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

Index: third_party/WebKit/Source/core/html/HTMLIFrameElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLIFrameElement.h b/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
index 7d27a3969e2c644ce79adc48a5bfbc9a2ce34ae0..3f82fc9e57286a82e9abe7949c4ab44f78749fa8 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
@@ -28,13 +28,17 @@
 #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);
@@ -75,6 +79,8 @@ class CORE_EXPORT HTMLIFrameElement final : public HTMLFrameElementBase {
 
   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;
   }
@@ -85,6 +91,7 @@ class CORE_EXPORT HTMLIFrameElement final : public HTMLFrameElementBase {
   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;