iframes with allowpaymentrequest attribute are allowed to make payment requests.

third_party/WebKit/Source/modules/payments/HTMLIFrameElementPayments.idl

Index: third_party/WebKit/Source/modules/payments/HTMLIFrameElementPayments.idl
diff --git a/third_party/WebKit/Source/modules/payments/HTMLIFrameElementPayments.idl b/third_party/WebKit/Source/modules/payments/HTMLIFrameElementPayments.idl
new file mode 100644
index 0000000000000000000000000000000000000000..27e8d15fba1ed2109f897dfa2571555b1913f977
--- /dev/null
+++ b/third_party/WebKit/Source/modules/payments/HTMLIFrameElementPayments.idl
@@ -0,0 +1,12 @@
+// Copyright 2016 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.
+
+// https://w3c.github.io/browser-payment-api/#paymentrequest-and-iframes
+// https://w3c.github.io/browser-payment-api/#paymentrequest-and-iframes

[please use gerrit instead, 2016/10/17 13:57:48]

Please remove the duplicate line.

[pals, 2016/10/18 04:39:21]

Messed up during rebase. Corrected now.

+
+[
+    RuntimeEnabled=PaymentRequest

[please use gerrit instead, 2016/10/17 13:57:48]

You don't need to specify 'ImplementedAs=HTMLIFrameElementPayments" here?

[pals, 2016/10/18 04:39:21]

As I see from existing blink code, if idl file name and implementation file
names are same, we do not need to specify ImplementedAs. 

+] partial interface HTMLIFrameElement {
+    [CEReactions, Reflect] attribute boolean allowPaymentRequest;
+};