iframes with allowpaymentrequest attribute are allowed to make payment requests.

third_party/WebKit/public/web/WebFrameOwnerProperties.h

Index: third_party/WebKit/public/web/WebFrameOwnerProperties.h
diff --git a/third_party/WebKit/public/web/WebFrameOwnerProperties.h b/third_party/WebKit/public/web/WebFrameOwnerProperties.h
index 375413821e940e8a03488db859f177dde7fe73c3..4ddf992eb84c1833957d8d0160ea46fc5e1e8f9a 100644
--- a/third_party/WebKit/public/web/WebFrameOwnerProperties.h
+++ b/third_party/WebKit/public/web/WebFrameOwnerProperties.h
@@ -19,6 +19,7 @@ struct WebFrameOwnerProperties {
   int marginWidth;
   int marginHeight;
   bool allowFullscreen;
+  bool allowPaymentRequest;
   WebString requiredCsp;
   WebVector<WebPermissionType> delegatedPermissions;
 
@@ -34,12 +35,14 @@ struct WebFrameOwnerProperties {
       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