MD Settings: Convert C++ handlers to be JavaScript-lifecycle aware.

chrome/browser/ui/webui/settings/downloads_handler.h

 // Copyright (c) 2015 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_DOWNLOADS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_DOWNLOADS_HANDLER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 
 namespace base {
 class Value;
 }
 
 namespace settings {
 
 // Chrome "Downloads" settings page UI handler.
 class DownloadsHandler : public SettingsPageUIHandler,
                          public ui::SelectFileDialog::Listener {
  public:
   DownloadsHandler();
   ~DownloadsHandler() override;
 
   // SettingsPageUIHandler implementation.
   void RegisterMessages() override;
+  void OnJavascriptAllowed() override {}
+  void OnJavascriptDisallowed() override {}
 
  private:
   // SelectFileDialog::Listener implementation.
   void FileSelected(const base::FilePath& path,
                     int index,
                     void* params) override;
 
   // Callback for the "selectDownloadLocation" message. This will prompt the
   // user for a destination folder using platform-specific APIs.
   void HandleSelectDownloadLocation(const base::ListValue* args);
 
   scoped_refptr<ui::SelectFileDialog> select_folder_dialog_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadsHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_DOWNLOADS_HANDLER_H_