iframes with allowpaymentrequest attribute are allowed to make payment requests.

third_party/WebKit/public/web/WebFrameOwnerProperties.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebFrameOwnerProperties_h
 #define WebFrameOwnerProperties_h
 
 #include "public/platform/WebString.h"
 #include "public/platform/WebVector.h"
 #include "public/platform/modules/permissions/WebPermissionType.h"
 #include <algorithm>
 
 namespace blink {
 
 struct WebFrameOwnerProperties {
   enum class ScrollingMode { Auto, AlwaysOff, AlwaysOn, Last = AlwaysOn };
 
   ScrollingMode scrollingMode;
   int marginWidth;
   int marginHeight;
   bool allowFullscreen;
+  bool allowPaymentRequest;
   WebString requiredCsp;
   WebVector<WebPermissionType> delegatedPermissions;
 
   WebFrameOwnerProperties()
       : scrollingMode(ScrollingMode::Auto),
         marginWidth(-1),
         marginHeight(-1),
         allowFullscreen(false) {}
 
 #if INSIDE_BLINK
   WebFrameOwnerProperties(
       ScrollbarMode scrollingMode,
       int marginWidth,
       int marginHeight,
       bool allowFullscreen,
+      bool allowPaymentRequest,
       const WebString& requiredCsp,
       const WebVector<WebPermissionType>& delegatedPermissions)
       : scrollingMode(static_cast<ScrollingMode>(scrollingMode)),
         marginWidth(marginWidth),
         marginHeight(marginHeight),
         allowFullscreen(allowFullscreen),
+        allowPaymentRequest(allowPaymentRequest),
         requiredCsp(requiredCsp),
         delegatedPermissions(delegatedPermissions) {}
 #endif
 };
 
 }  // namespace blink
 
 #endif