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

ios/chrome/browser/payments/js_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/js_payment_request_manager.h"
 
 #include "base/json/json_writer.h"
 #include "base/json/string_escape.h"
-#include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/values.h"
 #include "ios/web/public/payments/payment_request.h"
 
 namespace {
 
 // Sanitizes |JSON| and wraps it in quotes so it can be injected safely in
 // JavaScript.
 NSString* JSONEscape(NSString* JSON) {
   return base::SysUTF8ToNSString(
       base::GetQuotedJSONString(base::SysNSStringToUTF8(JSON)));
 }
 
 }  // namespace
 
 @interface JSPaymentRequestManager ()
 
 // Executes the JavaScript in |script| and passes a BOOL to |completionHandler|
 // indicating whether an error occurred. The resolve and reject functions in the
 // Payment Request JavaScript do not return values so the result is ignored.
 - (void)executeScript:(NSString*)script
     completionHandler:(void (^)(BOOL))completionHandler;
 
 @end
 
 @implementation JSPaymentRequestManager
 
+- (void)executeNoop {
+  [self executeScript:@"Function.prototype()" completionHandler:nil];
+}
+
 - (void)resolveRequestPromise:(const web::PaymentResponse&)paymentResponse
             completionHandler:(void (^)(BOOL))completionHandler {
   std::unique_ptr<base::DictionaryValue> paymentResponseData =
       paymentResponse.ToDictionaryValue();
   std::string paymentResponseDataJSON;
   base::JSONWriter::Write(*paymentResponseData, &paymentResponseDataJSON);
   NSString* script = [NSString
       stringWithFormat:
           @"__gCrWeb['paymentRequestManager'].pendingRequest.resolve(%@)",
           base::SysUTF8ToNSString(paymentResponseDataJSON)];
   [self executeScript:script completionHandler:completionHandler];
 }
 
 - (void)rejectRequestPromise:(NSString*)errorMessage
            completionHandler:(void (^)(BOOL))completionHandler {
   NSString* script = [NSString
       stringWithFormat:
           @"__gCrWeb['paymentRequestManager'].pendingRequest.reject(%@)",
           JSONEscape(errorMessage)];
   [self executeScript:script completionHandler:completionHandler];
 }
 
 - (void)resolveResponsePromise:(void (^)(BOOL))completionHandler {
   NSString* script =
       @"__gCrWeb['paymentRequestManager'].pendingResponse.resolve()";
   [self executeScript:script completionHandler:completionHandler];
 }
 
-- (void)rejectResponsePromise:(NSString*)errorMessage
-            completionHandler:(void (^)(BOOL))completionHandler {
-  NSString* script = [NSString
-      stringWithFormat:
-          @"__gCrWeb['paymentRequestManager'].pendingResponse.reject(%@)",
-          JSONEscape(errorMessage)];
-  [self executeScript:script completionHandler:completionHandler];
-}
-
 - (void)executeScript:(NSString*)script
     completionHandler:(void (^)(BOOL))completionHandler {
   [self executeJavaScript:script
         completionHandler:^(id result, NSError* error) {
           if (completionHandler)
             completionHandler(!error);
         }];
 }
 
 #pragma mark - Protected methods
 
 - (NSString*)scriptPath {
   return @"payment_request_manager";
 }
 
 - (NSString*)presenceBeacon {
   return @"__gCrWeb.paymentRequestManager";
 }
 
 @end