iframes with allowpaymentrequest attribute are allowed to make payment requests.

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

Index: third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp b/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
index f38e945a144e2cd9e5108e8014fc5b2903312d36..44eb13f6006d21547bb956f7bb66f57f29a735f7 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
@@ -118,6 +118,11 @@ void HTMLIFrameElement::parseAttribute(const QualifiedName& name,
     m_allowFullscreen = !value.isNull();
     if (m_allowFullscreen != oldAllowFullscreen)
       frameOwnerPropertiesChanged();
+  } else if (name == allowpaymentrequestAttr) {
+    bool oldAllowPaymentRequest = m_allowPaymentRequest;
+    m_allowPaymentRequest = !value.isNull();
+    if (m_allowPaymentRequest != oldAllowPaymentRequest)
+      frameOwnerPropertiesChanged();
   } else if (name == permissionsAttr) {
     if (initializePermissionsAttribute())
       m_permissions->setValue(value);