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

ios/chrome/browser/payments/payment_request_manager.mm

 // 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.
 
 #import "ios/chrome/browser/payments/payment_request_manager.h"
 
 #include "base/ios/ios_util.h"
 #import "base/ios/weak_nsobject.h"
 #import "base/mac/bind_objc_block.h"
 #include "base/mac/foundation_util.h"
@@ skipping 14 matching lines @@
 #include "ios/web/public/ssl_status.h"
 #import "ios/web/public/url_scheme_util.h"
 #import "ios/web/public/web_state/crw_web_view_proxy.h"
 #import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
 #include "ios/web/public/web_state/url_verification_constants.h"
 #include "ios/web/public/web_state/web_state.h"
 
 namespace {
 // Command prefix for injected JavaScript.
 const std::string kCommandPrefix = "paymentRequest";
+
+// Time interval between attempts to unblock the webview's JS event queue.
+const NSTimeInterval kNoopInterval = 0.1;
+
+// Time interval before closing the UI if the page has not yet called
+// PaymentResponse.complete().
+const NSTimeInterval kTimeoutInterval = 60.0;
+
 }  // namespace
 
 @interface PaymentRequestManager ()<PaymentRequestCoordinatorDelegate,
                                     PaymentRequestWebStateDelegate> {
   // View controller used to present the PaymentRequest view controller.
   base::WeakNSObject<UIViewController> _baseViewController;
 
   // PersonalDataManager used to manage user credit cards and addresses.
   autofill::PersonalDataManager* _personalDataManager;
 
@@ skipping 13 matching lines @@
   // Boolean to track if the script has been injected in the current page. This
   // is a faster check than asking the JS controller.
   BOOL _isScriptInjected;
 
   // True when close has been called and the PaymentRequest coordinator has
   // been destroyed.
   BOOL _closed;
 
   // Coordinator used to create and present the PaymentRequest view controller.
   base::scoped_nsobject<PaymentRequestCoordinator> _paymentRequestCoordinator;
+
+  // Timer used to periodically unblock the webview's JS event queue.
+  base::scoped_nsobject<NSTimer> _unblockEventQueueTimer;
+
+  // Timer used to close the UI if the page does not call
+  // PaymentResponse.complete() in a timely fashion.
+  base::scoped_nsobject<NSTimer> _paymentResponseTimeoutTimer;
 }
 
 // Synchronous method executed by -asynchronouslyEnablePaymentRequest:
 - (void)doEnablePaymentRequest:(BOOL)enabled;
 
 // Initialize the PaymentRequest JavaScript.
 - (void)initializeWebViewForPaymentRequest;
 
 // Handler for injected JavaScript callbacks.
 - (BOOL)handleScriptCommand:(const base::DictionaryValue&)JSONCommand;
@@ skipping 197 matching lines @@
 
   [_paymentRequestCoordinator start];
 
   return YES;
 }
 
 - (BOOL)handleResponseComplete {
   // TODO(crbug.com/602666): Check that there *is* a pending response here.
   // TODO(crbug.com/602666): Indicate success or failure in the UI.
 
+  [_unblockEventQueueTimer invalidate];
+  [_paymentResponseTimeoutTimer invalidate];
+
   [self dismissUI];
 
-  // TODO(crbug.com/602666): Reject the promise on failure.
   [_paymentRequestJsManager resolveResponsePromise:nil];
 
   return YES;
 }
 
 - (void)dismissUI {
   [_paymentRequestCoordinator stop];
   _paymentRequestCoordinator.reset();
 }
 
@@ skipping 17 matching lines @@
 #pragma mark - PaymentRequestCoordinatorDelegate methods
 
 - (void)paymentRequestCoordinatorDidCancel {
   [self cancelRequest];
 }
 
 - (void)paymentRequestCoordinatorDidConfirm:
     (web::PaymentResponse)paymentResponse {
   [_paymentRequestJsManager resolveRequestPromise:paymentResponse
                                 completionHandler:nil];
+
+  // Establish a timer that periodically prompts the JS manager to execute a
+  // noop. This works around an issue where the JS event queue is blocked while
+  // presenting the Payment Request UI.
+  _unblockEventQueueTimer.reset(
+      [[NSTimer scheduledTimerWithTimeInterval:kNoopInterval
+                                        target:_paymentRequestJsManager
+                                      selector:@selector(executeNoop)
+                                      userInfo:nil
+                                       repeats:YES] retain]);

[Moe, 2017/01/16 21:52:58]

is executeNoop what fixes the landscape issue? Why is it only necessary after
the payment is completed? 

[Justin Donnelly, 2017/01/18 19:36:21]

Correct, this fixes the landscape issue. Switching orientation is one thing that
causes the event queue to wake up, but it turns out that any messaging to the
web view also solves the issue.

It's necessary when the user hits the Pay button, which is what this method is
handling. At that point, the PR.show() promise is resolved and that's when the
page may do some asynchronous work (xhr or setTimeout simulating same).

+
+  // Per the spec, if the page does not call PaymentResponse.complete() within
+  // some timeout period, user agents may behave as if the complete() method was
+  // called with no arguments.
+  _paymentResponseTimeoutTimer.reset(
+      [[NSTimer scheduledTimerWithTimeInterval:kTimeoutInterval
+                                        target:self
+                                      selector:@selector(handleResponseComplete)
+                                      userInfo:nil
+                                       repeats:NO] retain]);
 }
 
 #pragma mark - PaymentRequestWebStateDelegate methods
 
 - (void)pageLoadedWithStatus:(web::PageLoadCompletionStatus)loadStatus {
   if (loadStatus != web::PageLoadCompletionStatus::SUCCESS)
     return;
 
   [self dismissUI];
   _isScriptInjected = NO;
   [self enableCurrentWebState];
 }
 
 @end