Adding a DownloadRestrictions group policy.

content/browser/download/download_manager_impl.cc

 // Copyright (c) 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.
 
 #include "content/browser/download/download_manager_impl.h"
 
 #include <iterator>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 343 matching lines @@
     }
     download = item_iterator->second.get();
   }
 
   base::FilePath default_download_directory;
   if (delegate_) {
     base::FilePath website_save_directory;  // Unused
     bool skip_dir_check = false;            // Unused
     delegate_->GetSaveDir(GetBrowserContext(), &website_save_directory,
                           &default_download_directory, &skip_dir_check);
+    if (delegate_->ShouldBlockAllDownloads())
+      info->result = DOWNLOAD_INTERRUPT_REASON_FILE_BLOCKED;
   }
 
   std::unique_ptr<DownloadFile> download_file;
 
   if (info->result == DOWNLOAD_INTERRUPT_REASON_NONE) {
     DCHECK(stream.get());
     download_file.reset(file_factory_->CreateFile(
         std::move(info->save_info), default_download_directory,
         std::move(stream), download->GetNetLogWithSource(),
         download->DestinationObserverAsWeakPtr()));
@@ skipping 359 matching lines @@
   if (delegate_)
     delegate_->OpenDownload(download);
 }
 
 void DownloadManagerImpl::ShowDownloadInShell(DownloadItemImpl* download) {
   if (delegate_)
     delegate_->ShowDownloadInShell(download);
 }
 
 }  // namespace content