Get rid of net::DO_NOT_PROMPT_FOR_LOGIN

ios/chrome/browser/net/image_fetcher.mm

 // Copyright 2012 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/net/image_fetcher.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 71 matching lines @@
     ImageFetchedCallback callback,
     const std::string& referrer,
     net::URLRequest::ReferrerPolicy referrer_policy) {
   DCHECK(request_context_getter_.get());
   net::URLFetcher* fetcher = net::URLFetcher::Create(url,
                                                      net::URLFetcher::GET,
                                                      this);
   downloads_in_progress_[fetcher] = [callback copy];
   fetcher->SetLoadFlags(
       net::LOAD_DO_NOT_SEND_COOKIES | net::LOAD_DO_NOT_SAVE_COOKIES |
-      net::LOAD_DO_NOT_SEND_AUTH_DATA | net::LOAD_DO_NOT_PROMPT_FOR_LOGIN);
+      net::LOAD_DO_NOT_SEND_AUTH_DATA);
   fetcher->SetRequestContext(request_context_getter_.get());
   fetcher->SetReferrer(referrer);
   fetcher->SetReferrerPolicy(referrer_policy);
   fetcher->Start();
 }
 
 void ImageFetcher::StartDownload(
     const GURL& url, ImageFetchedCallback callback) {
   ImageFetcher::StartDownload(
       url, callback, std::string(), net::URLRequest::NEVER_CLEAR_REFERRER);
@@ skipping 66 matching lines @@
     NSData* data) {
   (callback.get())(url, http_response_code, data);
 }
 
 void ImageFetcher::SetRequestContextGetter(
     const scoped_refptr<net::URLRequestContextGetter>& request_context_getter) {
   request_context_getter_ = request_context_getter;
 }
 
 }  // namespace image_fetcher