Add canMakeActivePayment() method to web payments.

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

Index: third_party/WebKit/Source/modules/payments/PaymentRequest.idl
diff --git a/third_party/WebKit/Source/modules/payments/PaymentRequest.idl b/third_party/WebKit/Source/modules/payments/PaymentRequest.idl
index c320eb7fb6df2f2e63fdf4e08415b079c00be169..5b88af6c3de862b1dd58f80e819723e2c5e789a3 100644
--- a/third_party/WebKit/Source/modules/payments/PaymentRequest.idl
+++ b/third_party/WebKit/Source/modules/payments/PaymentRequest.idl
@@ -2,7 +2,7 @@
 // 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-interface
+// https://w3c.github.io/browser-payment-api/
 // http://crbug.com/587995
 
 [
@@ -22,4 +22,8 @@
 
     attribute EventHandler onshippingaddresschange;
     attribute EventHandler onshippingoptionchange;
+
+    // https://github.com/zkoch/zkoch.github.io/blob/master/pr-detect-avail.md
+    // https://github.com/w3c/browser-payment-api/issues/310
+    [CallWith=ScriptState, RuntimeEnabled=CanMakeActivePayment] Promise<bool> canMakeActivePayment();
 };