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 bd19ff853c8aff215fc9703c273444f24058b286..efea369f459c68f5abc53697280f3a05ccdddecc 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
@@ -48,6 +48,7 @@ DEFINE_TRACE(HTMLIFrameElement) {
   visitor->trace(m_sandbox);
   visitor->trace(m_permissions);
   HTMLFrameElementBase::trace(visitor);
+  Supplementable<HTMLIFrameElement>::trace(visitor);
 }
 
 HTMLIFrameElement::~HTMLIFrameElement() {}
@@ -119,6 +120,11 @@ 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);