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..8346a9149ca7a1de335b947120249073df73aa78 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);