Adding a DownloadRestrictions group policy.

content/public/browser/download_manager_delegate.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/public/browser/download_manager_delegate.h"
 
+#include <string>
+
 #include "content/public/browser/download_item.h"
 
 namespace content {
 
 void DownloadManagerDelegate::GetNextId(const DownloadIdCallback& callback) {
   callback.Run(content::DownloadItem::kInvalidId);
 }
 
 bool DownloadManagerDelegate::DetermineDownloadTarget(
     DownloadItem* item,
@@ skipping 21 matching lines @@
   return false;
 }
 
 std::string
 DownloadManagerDelegate::ApplicationClientIdForFileScanning() const {
   return std::string();
 }
 
 DownloadManagerDelegate::~DownloadManagerDelegate() {}
 
+bool DownloadManagerDelegate::ShouldBlockAllDownloads() const {

[asanka, 2017/02/09 19:25:01]

Let's do all the blocking in //chrome.

[MAD, 2017/02/14 18:15:48]

Can you point me where //chrome could block the download early enough yet still
show the UI?

+  return false;
+}
+
 }  // namespace content