iframes with allowpaymentrequest attribute are allowed to make payment requests.

third_party/WebKit/Source/core/frame/FrameOwner.h

Index: third_party/WebKit/Source/core/frame/FrameOwner.h
diff --git a/third_party/WebKit/Source/core/frame/FrameOwner.h b/third_party/WebKit/Source/core/frame/FrameOwner.h
index 23f716a89ee317b4fab3298f9f39563e5d25a75a..e8716317a974f9a1e4bc706c777518a6e5e884a6 100644
--- a/third_party/WebKit/Source/core/frame/FrameOwner.h
+++ b/third_party/WebKit/Source/core/frame/FrameOwner.h
@@ -41,6 +41,7 @@ class CORE_EXPORT FrameOwner : public GarbageCollectedMixin {
   virtual int marginWidth() const = 0;
   virtual int marginHeight() const = 0;
   virtual bool allowFullscreen() const = 0;
+  virtual bool allowPaymentRequest() const = 0;
   virtual AtomicString csp() const = 0;
   virtual const WebVector<WebPermissionType>& delegatedPermissions() const = 0;
 };
@@ -65,6 +66,7 @@ class CORE_EXPORT DummyFrameOwner
   int marginWidth() const override { return -1; }
   int marginHeight() const override { return -1; }
   bool allowFullscreen() const override { return false; }
+  bool allowPaymentRequest() const override { return false; }
   AtomicString csp() const override { return nullAtom; }
   const WebVector<WebPermissionType>& delegatedPermissions() const override {
     DEFINE_STATIC_LOCAL(WebVector<WebPermissionType>, permissions, ());