Add a timeout if the page doesn't call complete() in a timely fashion.

ios/chrome/browser/payments/js_payment_request_manager.h

Index: ios/chrome/browser/payments/js_payment_request_manager.h
diff --git a/ios/chrome/browser/payments/js_payment_request_manager.h b/ios/chrome/browser/payments/js_payment_request_manager.h
index 812858aa880c76051d748e727c7b9edf1a1524af..ef4164f73bde04ba95e8d66ebd3b834f0e676f10 100644
--- a/ios/chrome/browser/payments/js_payment_request_manager.h
+++ b/ios/chrome/browser/payments/js_payment_request_manager.h
@@ -15,6 +15,10 @@ class PaymentResponse;
 // an app-side interface for interacting with it.
 @interface JSPaymentRequestManager : CRWJSInjectionManager
 
+// Executes a JS noop function. This is used to work around an issue where the
+// JS event queue is blocked while presenting the Payment Request UI.
+- (void)executeNoop;
+
 // Resolves the JavaScript promise associated with the current PaymentRequest
 // with the a JSON serialization of |paymentResponse|. |completionHandler| will
 // be invoked after the operation has completed with YES if successful.
@@ -32,11 +36,9 @@ class PaymentResponse;
 // YES if successful.
 - (void)resolveResponsePromise:(void (^)(BOOL))completionHandler;
 
-// Rejects the JavaScript promise associated with the current PaymentResponse
-// with the supplied |errorMessage|. |completionHandler| will be invoked after
-// the operation has completed with YES if successful.
-- (void)rejectResponsePromise:(NSString*)errorMessage
-            completionHandler:(void (^)(BOOL))completionHandler;
+// Note that there is no rejectResponsePromise method because the spec includes
+// no provision for rejecting the response promise. User agents are directed to
+// always resolve the promise.
 
 @end